Prior exercise training improves the outcome of acute myocardial infarction in the rat

Premorbid physical activity and prognosis after incident myocardial infarction: The atherosclerosis risk in communities study

BACKGROUND

High to moderate levels of physical activity (PA) are associated with low risk of incident cardiovascular disease. However, it is unclear whether the benefits of PA in midlife extend to cardiovascular health following myocardial infarction (MI) in later life.

METHODS

Among 1,111 Atherosclerosis Risk in Communities study participants with incident MI during Atherosclerosis Risk in Communities follow-up (mean age 73 [SD 9] years at MI, 54% men, 21% Black), PA on average 11.9 (SD 6.9) years prior to incident MI (premorbid PA) was evaluated as the average score of PA between visit 1 (1987-1989) and visit 3 (1993-1995) using a modified Baecke questionnaire. Total and domain-specific PA (sport, nonsport leisure, and work PA) was analyzed for associations with composite and individual outcomes of mortality, recurrent MI, and stroke after index MI using multivariable Cox models.

RESULTS

During a median follow-up of 4.6 (IQI 1.0-10.5) years after incident MI, 823 participants (74%) developed a composite outcome. The 10-year cumulative incidence of the composite outcome was lower in the highest, as compared to the lowest tertile of premorbid total PA (56% vs. 70%, respectively). This association remained statistically significant even after adjusting for potential confounders (adjusted hazard ratio [aHR] 0.80 [0.67-0.96] for the highest vs. lowest tertile). For individual outcomes, high premorbid total PA was associated with a low risk of recurrent MI (corresponding aHR 0.64 [0.44, 0.93]). When domain-specific PA was analyzed, similar results were seen for sport and work PA. The association was strongest in the first year following MI (e.g., aHR of composite outcome 0.66 [95% CI 0.47, 0.91] for the highest vs. lowest tertile of total PA).

CONCLUSIONS

Premorbid PA was associated positively with post-MI cardiovascular health. Our results demonstrate the additional prognostic advantages of PA beyond reducing the risk of incident MI.

The Enhanced Effects of Swimming and Running Preconditioning in an Experimental Model of Myocardial Ischemia/Reperfusion Injury

Background and Objectives: This study was conducted to examine the influence of different swimming and running protocols as forms of physiological preconditioning on an isolated rat heart's ischemia/reperfusion injury. Materials and Methods: This study was conducted on 60 male Wistar albino rats (6 weeks old, bw: 200 ± 20 g), divided into: CTRL group-a sedentary control group; sAeT-a group that underwent aerobic swimming conditioning using a swimming protocol for 8 weeks; sAnT-a group that underwent anaerobic swimming conditioning; rAeT-a group that underwent aerobic running conditioning; and rAnT-a group that underwent anaerobic running conditioning. After the preconditioning protocols, ex vivo estimating of myocardial function according to the Langendorff technique was performed. Results: The anaerobic running training decreased heart rate and the anaerobic swimming training reduced coronary flow, demonstrating the difference in the physiological heart response of aerobic/anaerobic physical training (p < 0.05). Heart rate was significantly reduced in both training swimming groups after a period of ischemia (p < 0.05). On the other hand, the anaerobic running protocol induced a significantly decreased heart rate in comparison with the aerobic running group and the sedentary group (p < 0.05). Conclusions: The data from this experimental study support many protective training effects, i.e., improved contractility, improved resting heart rate, and increased physical work capacity and exercise tolerance. Physical training in the form of anaerobic running induces greater heart preconditioning for reperfusion injury in comparison with anaerobic swimming training.

New Approaches in Heart Research: Prevention Instead of Cardiomyoplasty?

Cardiovascular diseases are the leading cause of death in industrialized nations. Due to the high number of patients and expensive treatments, according to the Federal Statistical Office (2017) in Germany, cardiovascular diseases account for around 15% of total health costs. Advanced coronary artery disease is mainly the result of chronic disorders such as high blood pressure, diabetes, and dyslipidemia. In the modern obesogenic environment, many people are at greater risk of being overweight or obese. The hemodynamic load on the heart is influenced by extreme obesity, which often leads to myocardial infarction (MI), cardiac arrhythmias, and heart failure. In addition, obesity leads to a chronic inflammatory state and negatively affects the wound-healing process. It has been known for many years that lifestyle interventions such as exercise, healthy nutrition, and smoking cessation drastically reduce cardiovascular risk and have a preventive effect against disorders in the healing process. However, little is known about the underlying mechanisms, and there is significantly less high-quality evidence compared to pharmacological intervention studies. Due to the immense potential of prevention in heart research, the cardiologic societies are calling for research work to be intensified, from basic understanding to clinical application. The topicality and high relevance of this research area are also evident from the fact that in March 2018, a one-week conference on this topic with contributions from top international scientists took place as part of the renowned "Keystone Symposia" ("New Insights into the Biology of Exercise"). Consistent with the link between obesity, exercise, and cardiovascular disease, this review attempts to draw lessons from stem-cell transplantation and preventive exercise. The application of state-of-the-art techniques for transcriptome analysis has opened new avenues for tailoring targeted interventions to very individual risk factors.

Animal Models of Exercise From Rodents to Pythons

Acute and chronic animal models of exercise are commonly used in research. Acute exercise testing is used, often in combination with genetic, pharmacological, or other manipulations, to study the impact of these manipulations on the cardiovascular response to exercise and to detect impairments or improvements in cardiovascular function that may not be evident at rest. Chronic exercise conditioning models are used to study the cardiac phenotypic response to regular exercise training and as a platform for discovery of novel pathways mediating cardiovascular benefits conferred by exercise conditioning that could be exploited therapeutically. The cardiovascular benefits of exercise are well established, and, frequently, molecular manipulations that mimic the pathway changes induced by exercise recapitulate at least some of its benefits. This review discusses approaches for assessing cardiovascular function during an acute exercise challenge in rodents, as well as practical and conceptual considerations in the use of common rodent exercise conditioning models. The case for studying feeding in the Burmese python as a model for exercise-like physiological adaptation is also explored.

Effects of swimming training on myocardial protection in rats

Swimming is important for promoting and maintaining health, as it can increase the efficiency of the cardiovascular system and decrease the occurrence of cardiovascular diseases. The objective of the present study was to examine whether swimming training could decrease myocardial injury in rats caused by myocardial ischemia/reperfusion (I/R). Sprague-Dawley rats were randomized into four groups, namely the Sham, coronary artery occlusion, swimming training and ischemic preconditioning (IPC) groups. Myocardial I/R was induced in anesthetized male Sprague-Dawley rats by a 40-min occlusion followed by a 3-h reperfusion of the left anterior descending coronary artery. The rats were sacrificed after surgery and their hearts were examined. The results demonstrated that the number of TUNEL-positive nuclei and degree of caspase-3 activation were both significantly increased in the myocardium following myocardial I/R in rats, indicating increased cardiomyocyte apoptosis. On the other hand, swimming training decreased the serum levels of creatine phosphokinase, lactate dehydrogenase and cardiac troponin I, and was associated with reduced histological damage and myocardial infarct size. Furthermore, swimming training also reduced TNF-α levels, caspase-3 activation and enhanced Bcl-2 activation, which decreased the number of apoptotic cells in the myocardium. The findings of the present study showed that swimming training and IPC could similarly decrease myocardial injury following myocardial I/R, and may therefore be used as exercise training to effectively prevent myocardial injury.

A Contemporary Review of the Effects of Exercise Training on Cardiac Structure and Function and Cardiovascular Risk Profile: Insights From Imaging

Exercise is a commonly prescribed therapy for patients with established cardiovascular disease or those at high risk for de novo disease. Exercise-based, multidisciplinary programs have been associated with improved clinical outcomes post myocardial infarction and is now recommended for patients with cancer at elevated risk for cardiovascular complications. Imaging studies have documented numerous beneficial effects of exercise on cardiac structure and function, vascular function and more recently on the cardiovascular risk profile. In this contemporary review, we will discuss the effects of exercise training on imaging-derived cardiovascular outcomes. For cardiac imaging via echocardiography or magnetic resonance, we will review the effects of exercise on left ventricular function and remodeling in patients with established or at risk for cardiac disease (myocardial infarction, heart failure, cancer survivors), and the potential utility of exercise stress to assess cardiac reserve. Exercise training also has salient effects on vascular function and health including the attenuation of age-associated arterial stiffness and thickening as assessed by Doppler ultrasound. Finally, we will review recent data on the relationship between exercise training and regional adipose tissue deposition, an emerging marker of cardiovascular risk. Imaging provides comprehensive and accurate quantification of cardiac, vascular and cardiometabolic health, and may allow refinement of risk stratification in select patient populations. Future studies are needed to evaluate the clinical utility of novel imaging metrics following exercise training.

Estrogen Deprivation and Myocardial Infarction: Role of Aerobic Exercise Training, Inflammation and Metabolomics

In general, postmenopausal women present higher mortality, and worse prognosis after myocardial infarction (MI) compared to men, due to estrogen deficiency. After MI, cardiovascular alterations occur such as the autonomic imbalance and the pro-inflammatory cytokines increase. In this sense, therapies that aim to minimize deleterious effects caused by myocardial ischemia are important. Aerobic training has been proposed as a promising intervention in the prevention of cardiovascular diseases. On the other hand, some studies have attempted to identify potential biomarkers for cardiovascular diseases or specifically for MI. For this purpose, metabolomics has been used as a tool in the discovery of cardiovascular biomarkers. Therefore, the objective of this work is to discuss the changes involved in ovariectomy, myocardial infarction, and aerobic training, with emphasis on inflammation and metabolism.

Aerobic training prevents cardiometabolic changes triggered by myocardial infarction in ovariectomized rats

This study aimed to evaluate the impact of aerobic training (AT) on autonomic, cardiometabolic, ubiquitin-proteasome activity, and inflammatory changes evoked by myocardial infarction (MI) in ovariectomized rats. Female Wistar rats were ovariectomized and divided into four groups: sedentary + sham (SS), sedentary + MI (SI), AT + sham surgery (TS), AT + MI (TI). AT was performed on a treadmill for 8 weeks before MI. Infarcted rats previously subjected to AT presented improved physical capacity, increased interleukin-10, and decreased pro-inflammatory cytokines. Metabolomic analysis identified and quantified 62 metabolites, 9 were considered significant by the Vip Score. SS, SI, and TS groups presented distinct metabolic profiles; however, TI could not be distinguished from the SS group. MI dramatically increased levels of dimethylamine, and AT prevented this response. Our findings suggest that AT may be useful in preventing the negative changes in functional, inflammatory, and metabolic parameters related to MI in ovariectomized rats.

Prior exercise training and experimental myocardial infarction: A systematic review and meta-analysis

Exercising prior to experimental infarction may have beneficial effects on the heart. The objective of this study was to analyze studies on animals that had exercised prior to myocardial infarction and to examine any benefits through a systematic review and meta-analysis. The databases MEDLINE, Google Scholar, and Cochrane were consulted. We analyzed articles published between January 1978 and November 2018. From a total of 858 articles, 13 manuscripts were selected in this review. When animals exercised before experimental infarction, there was a reduction in mortality, a reduction in infarct size, improvements in cardiac function, and a better molecular balance between genes and proteins that exhibit cardiac protective effects. Analyzing heart weight/body weight, we observed the following results - Mean difference 95% CI - -0.02 [-0.61,0.57]. Meta-analysis of the infarct size (% of the left ventricle) revealed a statistically significant decrease in the size of the infarction in animals that exercised before myocardial infarction, in comparison with the sedentary animals -5.05 [-7.68, -2.40]. Analysis of the ejection fraction, measured by echo (%), revealed that animals that exercised before myocardial infarction exhibited higher and statistically significant measures, compared with sedentary animals 8.77 [3.87,13.66]. We conclude that exercise performed prior to experimental myocardial infarction confers cardiac benefits to animals.

The greater effect of high-intensity interval training versus moderate-intensity continuous training on cardioprotection against ischemia-reperfusion injury through Klotho levels and attenuate of myocardial TRPC6 expression

BACKGROUND

Myocardial ischemia-reperfusion (IR) injury is a leading cause of death all over the world, so developing practical approaches to promote cardioprotection against IR injury is essential. Exercise training is an effective strategy to improve cardioprotection. Hence, the purpose of this study was to investigate the effect of short-term preconditioning with two types of high-intensity interval training (HIIT) and moderate intensity continuous training (MICT) on klotho and TRPC6 mechanisms in cardioprotection.

METHODS

Eighty Male Wistar rats (250-300 g) were randomly divided into 7 groups, including Control, HIIT, MICT, Sham, IR, HIIT+IR, and MICT+IR. Training was performed in 5 consecutive days. HIIT protocol consisted of running on the treadmill at intervals 85-90% vo2max that separated by slow intensity periods at 50-60% vo2max. MICT program was performed at 70% VO2max at the same running distance with HIIT groups. The cardiac IR injury was induced by LAD occlusion followed by reperfusion. ELISA kit was used in order to measure the plasma levels of klotho, LDH and CK-MB, and TRPC6 expression was determined using the western blot technique. Data were analyzed using one way ANOVA and Tukey's post hoc tests.

RESULTS

The results of this study showed that both types of exercise training programs significantly increase plasma levels of klotho and reduce the infarct size and heart injury. In addition, the exercise training decreased the amount of TRPC6 channels expression during IR. However, the effect of HIIT on increasing the klotho and cardioprotection was greater compared to MICT.

CONCLUSIONS

Based on the results, even a short-term of aerobic exercise training, especially HIIT, promotes cardioprotection against IR injury and decreases infarct size via an increase in klotho and attenuate of protein expression of myocardial TRPC6 during IR.

Trimetazidine combined with exercise improves exercise capacity and anti-fatal stress ability through enhancing mitochondrial quality control

AIMS

To explore the effects of trimetazidine combined with exercise on EC and anti-fatal stress ability, and illustrate the underlying mechanism.

METHODS

C57BL/6 mice were randomly assigned to four groups (n = 11 in each group): the control, exercise, trimetazidine and trimetazidine + exercise (TE) groups. Mice were accordingly given saline (ig), Aerobic exercise (AE), trimetazidine (ig), or a combination of trimetazidine (ig) and AE for five weeks. After the intervention, each group was randomly subdivided into rest and exhaustive exercise (EE) subgroups. The mice in the control-EE and TE-EE subgroups underwent fatal stress experiments. EC and anti-fatal stress ability were assessed respectively. Mitochondrial quality control (MQC) in skeletal muscle were measured at the protein level and the organelle level.

KEY FINDINGS

A significantly increased exhaustive swimming time was observed in exercise (39.10 ± 12.58 min vs 14.18 ± 4.37 min), trimetazidine (33.73 ± 8.45 min vs 14.18 ± 4.37 min) and TE groups (73.78 ± 18.95 min vs 14.18 ± 4.37 min) compared with that in the control group, and a synergistic effect was detected (P < 0.05). Fatal stress experiments successfully induced skeletal muscle damage, including increased creatine kinase activity, myofibrosis, and impaired antioxidative enzyme system, all those were significantly alleviated by trimetazidine supplementation combined with AE precondition (P < 0.05). Meanwhile, AE and trimetazidine alone or combined, significantly enhanced the MQC in normal mice by activating mitochondrial biogenesis, dynamics and mitophagy, and that in mice underwent fatal stress stimulus (P < 0.05).

SIGNIFICANCE

This study for the first time found that trimetazidine and AE have synergistic effects on improving EC. Moreover, the combination of both interventions enhances anti-fatal stress ability. Enhancing MQC may be a key mechanism of AE combined with trimetazidine that improves EC and anti-fatal stress ability.

Exercise Training Potentiates The Cardioprotective Effects of Stem Cells Post-infarction

BACKGROUND

Preconditioning of cell recipients may exert a significant role in attenuating the hostility of the infarction milieu, thereby enhancing the efficacy of cell therapy. This study was conducted to examine whether exercise training potentiates the cardioprotective effects of adipose-derived stem cell (ADSC) transplantation following myocardial infarction (MI) in rats.

METHODS

Four groups of female Fisher-344 rats were studied: Sham; non-trained rats with MI (sMI); non-trained rats with MI submitted to ADSCs transplantation (sADSC); trained rats with MI submitted to ADSCs (tADSC). Rats were trained 9 weeks prior to MI and ADSCs transplantation. Echocardiography was applied to assess cardiac function. Myocardial performance was evaluated in vitro. Protein expression analyses were carried out by immunoblotting. Periodic acid-Schiff staining was used to analyse capillary density and apoptosis was evaluated with terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay.

RESULTS

Echocardiography performed 4 weeks after the infarction revealed attenuated scar size in the both sADSC and tADSC groups compared to the sMI group. However, fractional shortening was improved only in the tADSC group. In vitro myocardial performance was similar between the tADSC and Sham groups. The expression of phosphoSer473Akt1 and VEGF were found to be higher in the hearts of the tADSC group compared to both the sADSC and sMI groups. Histologic analysis demonstrated that tADSC rats had higher capillary density in the remote and border zones of the infarcted sites compared to the sMI rats.

CONCLUSIONS

Preconditioning with exercise induces a pro-angiogenic milieu that may potentiate the therapeutic effects of ADSCs on cardiac remodelling following MI.

BDNF contributes to the skeletal muscle anti-atrophic effect of exercise training through AMPK-PGC1α signaling in heart failure mice

INTRODUCTION

Exercise training is a coadjuvant therapy in preventive cardiology, and it delays cardiac dysfunction and exercise intolerance in heart failure (HF). However, the mechanisms underlying muscle function improvement and cardioprotection are poorly understood. In this study, we tested whether exercise training would counteract skeletal muscle atrophy via activation of the BDNF pathway in myocardial infarction (MI)-induced HF mice.

MATERIAL AND METHODS

A cohort of male Sham-operated and MI mice were assigned into 8-week moderate exercise training, and untrained counterparters were used as control. Exercise capacity, plasma norepinephrine (NE) level, heart rate (HR), fractional shortening (FS) and ejection fraction (EF) were measured. The protein expression of BDNF, p-TrkB, p-AMPK and PGC1α were analyzed by Western blot.

RESULTS

Compared with the Sham-operated mice, MI mice displayed reduced total distance run and elevated plasma NE level (both p < 0.05). Exercise training significantly improved distance run and plasma NE levels in HF mice (both p < 0.05). Significantly increased HR, decreased FS and EF were observed in the MI group as compared to the Sham-operated group, and exercise training prevent the hemodynamic status and systolic dysfunction in MI mice (all p < 0.05). The expression of BDNF, p-TrkB, p-AMPK and PGC1α were significantly decreased in the skeletal muscle from MI compared to Sham-operated mice, which were significantly increased by exercise training (all p < 0.05). In addition, BDNF siRNA markedly decreased the protein level of p-AMPK and PGC1α in C2C12 myoblasts.

CONCLUSIONS

Taken together, our data provide evidence for exercise training may counteract HF-induced muscle atrophy through induced activation of BDNF pathway.

Exercise training provides cardioprotection by activating and coupling endothelial nitric oxide synthase via a β3-adrenergic receptor-AMP-activated protein kinase signaling pathway

Exercise training confers sustainable protection against ischemia/reperfusion injury. However, the mechanism by which this process occurs is not fully understood. Previously, it was shown that β₃-adrenergic receptors (β₃-ARs) play a critical role in regulating the activation of endothelial nitric oxide synthase (eNOS) in response to exercise and play a critical role in exercise-mediated cardioprotection. Intriguingly, a deficiency in β₃-ARs led to increased myocardial injury following exercise training. The purpose of the current study was to determine mechanisms by which β₃-ARs are linked to eNOS activation and to determine the mechanism responsible for the exacerbated ischemia/reperfusion injury displayed by β₃-AR deficient (β₃-AR KO) mice after exercise training. Wild-type (n = 37) and β₃-AR KO (n = 40) mice were subjected to voluntary wheel running for 4 weeks. Western blot analysis revealed that neither protein kinase B nor protein kinase A linked β₃-ARs to eNOS following exercise training. However, analysis revealed a role for AMP-activated protein kinase (AMPK). Specifically, exercise training increased the phosphorylation of AMPK in the hearts of wild-type mice, but failed to do so in the hearts of β₃-AR KO mice. Additional studies revealed that exercise training rendered eNOS less coupled and increased NOS-dependent superoxide levels in β₃-AR KO mice. Finally, supplementing β₃-AR KO mice with the eNOS coupler, tetrahydrobiopterin, during the final week of exercise training reduced myocardial infarction. These findings provide important information that exercise training protects the heart in the setting of myocardial ischemia/reperfusion injury by activating and coupling eNOS via the stimulation of a β₃-AR-AMPK signaling pathway.

Aerobic training prior to myocardial infarction increases cardiac GLUT4 and partially preserves heart function in spontaneously hypertensive rats

We assessed cardiac function (echocardiographic) and glucose transporter 4 (GLUT4) expression (Western blot) in response to 10 weeks of aerobic training (treadmill) prior to acute myocardial infarction (AMI) by ligation of the left coronary artery in spontaneously hypertensive rats. Animals were allocated to sedentary+sham, sedentary+AMI, training+sham, and training+AMI. Aerobic training prior to AMI partially preserves heart function. AMI and/or aerobic training increased GLUT4 expression. However, those animals trained prior to AMI showed a greater increase in GLUT4 in cardiomyocytes.

Decreased physical activity is a predictor for a complicated recovery post cardiac surgery

Background

Physical activity (PA) reduces the risk of cardiovascular disease and physically active survivors of a cardiac event are at lower risk of recurrent events. We hypothesized that patients with a decreased PA, undergoing cardiac surgery, are at higher risk for a postoperative complicated recovery (PCR).

Methods

Three thousand three hundred eighty two patients undergoing elective cardiac surgery between January 2007 and December 2013 were included. The group was divided into three subgroups: group A, aged ≤ 65 years (N = 1329); group B, aged > 65 years and ≤ 75 years (N = 1250); and group C aged >75 years (N = 803). To assess PA, the criteria of the Corpus Christy Heart Project were used. A PCR consists of the occurrence of a major postoperative event, defined as any of the following complications: reoperation, deep sternal wound infection, renal failure, stroke, postoperative ventilation > 2 days, intensive care stay ≥ 5 days, hospital stay ≥ 10 days, or hospital mortality.

Results

One thousand three hundred sixty seven patients (40%) were considered as patients with a decreased PA. Both in group B (p = 0.001) and in group C (p = 0.003), patients with a decreased PA were significantly associated with an increased risk of a PCR, which was not the case in group A (p = 0.28). Logistic regression analysis identified a decreased PA as an independent predictor for PCR in groups B (p = 0.003, odds 1.71) and C (p = 0.033, odds 1.48), but not in group A (p = 0.11, odds 0.71).

Conclusion

Decreased physical activity is an independent predictor for a PCR in patients aged 65 years or older undergoing elective cardiac surgery.

Preventive aerobic training exerts a cardioprotective effect on rats treated with monocrotaline

Pulmonary arterial hypertension (PAH) is a chronic disease which causes overload to the right ventricle. The effect of preventive training on cardiac remodelling in this condition is still unknown. This study aimed to evaluate the influence of preventive training on hypertrophy, heart function and gene expression of calcium transport proteins in rats with monocrotaline-induced PAH. Thirty-two male Wistar rats were randomly divided into four groups: S, sedentary control; T, trained control; SM, sedentary monocrotaline; and TM, trained monocrotaline. The preventive training protocol was performed on a treadmill for 13 weeks, five times/week. The first two weeks were adopted for adaptation to training with gradual increases in speed/time. The speed of the physical training from the third to tenth weeks was gradually increased from 0.9 to 1.1 km/h for 60 min. Next, monocrotaline was applied (60 mg/kg) to induce PAH and lactate threshold analysis performed to determine the training speeds. The training speed of the TM group in the following two weeks was 0.8 km/h for 60 min and the T = 0.9 km/h for 60 min; in the final two weeks, both groups trained at the same speed and duration 0.9 km/h, 60 min. Cardiac function was assessed through echocardiography, ventricular hypertrophy through histomorphometric analysis and gene expression through RT-qPCR. Right cardiac function assessed through the peak flow velocity was SM = 75.5 cm/s vs. TM = 92.0 cm/s (P = 0.001), and ventricular hypertrophy was SM = 106.4 μm² vs. TM = 77.7 μm² (P = 0.004). There was a decrease in the gene expression of ryanodine S = 1.12 au vs. SM = 0.60 au (P = 0.02) without alterations due to training. Thus, we conclude that prior physical training exerts a cardioprotective effect on the right ventricle in the monocrotaline rat model.

Previous exercise training increases levels of PPAR-α in long-term post-myocardial infarction in rats, which is correlated with better inflammatory response

OBJECTIVE

Exercise is a protective factor for cardiovascular morbidity and mortality, with unclear mechanisms. Changing the myocardial metabolism causes harmful consequences for heart function and exercise contributes to metabolic adjustment modulation. Peroxisome proliferator-activated receptors (PPARs) are also myocardium metabolism regulators capable of decreasing the inflammatory response. We hypothesized that PPAR-α is involved in the beneficial effects of previous exercise on myocardial infarction (MI) and cardiac function, changing the expression of metabolic and inflammatory response regulators and reducing myocardial apoptosis, which partially explains the better outcome.

METHODS AND RESULTS

Exercised rats engaged in swimming sessions for 60 min/day, 5 days/week, for 8 weeks. Both the exercised rats and sedentary rats were randomized to MI surgery and followed for 1 week (EI1 or SI1) or 4 weeks (EI4 or SI4) of healing or to sham groups. Echocardiography was employed to detect left ventricular function and the infarct size. Additionally, the TUNEL technique was used to assess apoptosis and immunohistochemistry was used to quantitatively analyze the PPAR-α, TNF-α and NF-κB antigens in the infarcted and non-infarcted myocardium. MI-related mortality was higher in SI4 than in EI4 (25% vs 12%), without a difference in MI size. SI4 exhibited a lower shortening fraction than EI4 did (24% vs 35%) and a higher apoptosis/area rate (3.97±0.61 vs 1.90±1.82) in infarcted areas (both p=0.001). Immunohistochemistry also revealed higher TNF-α levels in SI1 than in EI1 (9.59 vs 4.09, p<0.001) in infarcted areas. In non-infarcted areas, EI4 showed higher levels of TNF-α and positive correlations between PPAR-α and NF-κB (r=0.75, p=0.02), in contrast to SI4 (r=0.05, p=0.87).

CONCLUSION

Previously exercised animals had better long-term ventricular function post-MI, in addition to lower levels of local inflammatory markers and less myocardial apoptosis, which seemed to be related to the presence of PPAR-α.

Experimental studies of the molecular pathways regulated by exercise and resveratrol in heart, skeletal muscle and the vasculature

Regular exercise contributes to healthy aging and the prevention of chronic disease. Recent research has focused on the development of molecules, such as resveratrol, that activate similar metabolic and stress response pathways as exercise training. In this review, we describe the effects of exercise training and resveratrol on some of the organs and tissues that act in concert to transport oxygen throughout the body. In particular, we focus on animal studies that investigate the molecular signaling pathways induced by these interventions. We also compare and contrast the effects of exercise and resveratrol in diseased states.

Cardioprotection afforded by exercise training prior to myocardial infarction is associated with autonomic function improvement

BACKGROUND

It has been suggested that exercise training (ET) protects against the pathological remodeling and ventricular dysfunction induced by myocardial infarction (MI). However, it remains unclear whether the positive adjustments on baroreflex and cardiac autonomic modulations promoted by ET may afford a cardioprotective mechanism. The aim of this study was to evaluate the effects of aerobic ET, prior to MI, on cardiac remodeling and function, as well as on baroreflex sensitivity and autonomic modulation in rats.

METHODS

Male Wistar rats were divided into 4 groups: sedentary rats submitted to Sham surgery (C); trained rats submitted to Sham surgery (TC); sedentary rats submitted to MI (I), trained rats submitted to MI (TI). Sham and MI were performed after ET period. After surgeries, echocardiographic, hemodynamic and autonomic (baroreflex sensitivity, cardiovascular autonomic modulation) evaluations were conducted.

RESULTS

Prior ET prevented an additional decline in exercise capacity in TI group in comparison with I. MI area was not modified by previous ET. ET was able to increase the survival and prevent additional left ventricle dysfunction in TI rats. Although changes in hemodynamic evaluations were not observed, ET prevented the decrease of baroreflex sensitivity, and autonomic dysfunction in TI animals when compared with I animals. Importantly, cardiac improvement was associated with the prevention of cardiac autonomic impairment in studied groups.

CONCLUSIONS

Prior ET was effective in changing aerobic capacity, left ventricular morphology and function in rats undergoing MI. Furthermore, these cardioprotective effects were associated with attenuated cardiac autonomic dysfunction observed in trained rats. Although these cause-effect relationships can only be inferred, rather than confirmed, our study suggests that positive adaptations of autonomic function by ET can play a vital role in preventing changes associated with cardiovascular disease, particularly in relation to MI.

Exercise protects against chronic β-adrenergic remodeling of the heart by activation of endothelial nitric oxide synthase

Extensive data have shown that exercise training can provide cardio-protection against pathological cardiac hypertrophy. However, how long the heart can retain cardio-protective phenotype after the cessation of exercise is currently unknown. In this study, we investigated the time course of the loss of cardio-protection after cessation of exercise and the signaling molecules that are responsible for the possible sustained protection. Mice were made to run on a treadmill six times a week for 4 weeks and then rested for a period of 0, 1, 2 and 4 weeks followed by isoproterenol injection for 8 days. Morphological, echocardiographic and hemodynamic changes were measured, gene reactivation was determined by real-time PCR, and the expression and phosphorylation status of several cardio-protective signaling molecules were analyzed by Western-blot. HW/BW, HW/TL and LW/BW decreased significantly in exercise training (ER) mice. The less necrosis and lower fetal gene reactivation induced by isoproterenol injection were also found in ER mice. The echocardiographic and hemodynamic changes induced by β-adrenergic overload were also attenuated in ER mice. The protective effects can be sustained for at least 2 weeks after the cessation of the training. Western-blot analysis showed that the alterations in the phosphorylation status of endothelial nitric oxide synthase (eNOS) (increase in serine 1177 and decrease in threonine 495) continued for 2 weeks after the cessation of the training whereas increases of the phosphorylation of Akt and mTOR disappeared. Further study showed that L-NG-Nitroarginine methyl ester (L-NAME) treatment abolished the cardio-protective effects of ER. Our findings demonstrate that stimulation of eNOS in mice through exercise training provides acute and sustained cardioprotection against cardiac hypertrophy.

Exercise training in adverse cardiac remodeling

Cardiac remodeling in response to a myocardial infarction or chronic pressure-overload is an independent risk factor for the development of heart failure. In contrast, cardiac remodeling produced by regular physical exercise is associated with a decreased risk for heart failure. There is evidence that exercise training has a beneficial effect on disease progression and survival in patients with cardiac remodeling and dysfunction, but concern has also been expressed that exercise training may aggravate pathological remodeling and dysfunction. Here we present studies from our laboratory into the effects of exercise training on pathological cardiac remodeling and dysfunction in mice. The results indicate that even in the presence of a large infarct, exercise training exerts beneficial effects on the heart. These effects were mimicked in part by endothelial nitric oxide synthase (eNOS) overexpression and abrogated by eNOS deficiency, demonstrating the importance of nitric oxide signaling in mediating the cardiac effects of exercise. Exercise prior to a myocardial infarction was also cardioprotective. In contrast, exercise tended to aggravate pathological cardiac remodeling and dysfunction in the setting of pressure-overload produced by an aortic stenosis. These observations emphasize the critical importance of the underlying pathological stimulus for cardiac hypertrophy and remodeling, in determining the effects of exercise training. Future studies are needed to define the influence of exercise type, intensity and duration in different models and severities of pathological cardiac remodeling. Together such studies will aid in optimizing the therapy of exercise training in the setting of cardiovascular disease.

Role of β-adrenergic receptors and nitric oxide signaling in exercise-mediated cardioprotection

Exercise promotes cardioprotection in both humans and animals not only by reducing risk factors associated with cardiovascular disease but by reducing myocardial infarction and improving survival following ischemia. This article will define the role that nitric oxide and β-adrenergic receptors play in mediating the cardioprotective effects of exercise in the setting of ischemia-reperfusion injury.

High inborn aerobic capacity does not protect the heart following myocardial infarction

Maximal oxygen uptake (Vo2max) is a strong prognostic marker for morbidity and mortality, but the cardio-protective effect of high inborn Vo2max remains unresolved. We aimed to investigate whether rats with high inborn Vo2max yield cardio-protection after myocardial infarction (MI) compared with rats with low inborn Vo2max. Rats breed for high capacity of running (HCR) or low capacity of running (LCR) were randomized into HCR-SH (sham), HCR-MI, LCR-SH, and LCR-MI. Vo2max was lower in HCR-MI and LCR-MI compared with respective sham (P < 0.01), supported by a loss in global cardiac function, assessed by echocardiography. Fura 2-AM loaded cardiomyocyte experiments revealed that HCR-MI and LCR-MI decreased cardiomyocyte shortening (39%, and 34% reduction, respectively, both P < 0.01), lowered Ca(2+) transient amplitude (37%, P < 0.01, and 20% reduction, respectively), and reduced sarcoplasmic reticulum (SR) Ca(2+) content (both; 20%, P < 0.01) compared with respective sham. Diastolic Ca(2+) cycling was impaired in HCR-MI and LCR-MI evidenced by prolonged time to 50% Ca(2+) decay that was partly explained by the 47% (P < 0.01) and 44% (P < 0.05) decrease in SR Ca(2+)-ATPase Ca(2+) removal, respectively. SR Ca(2+) leak increased by 177% in HCR-MI (P < 0.01) and 67% in LCR-MI (P < 0.01), which was abolished by inhibition of Ca(2+)/calmodulin-dependent protein kinase II. This study demonstrates that the effect of MI in HCR rats was similar or even more pronounced on cardiac- and cardiomyocyte contractile function, as well as on Ca(2+) handling properties compared with observations in LCR. Thus our data do not support a cardio-protective effect of higher inborn aerobic capacity.

Exercise training-enhanced, endothelium-dependent dilation mediated by altered regulation of BK(Ca) channels in collateral-dependent porcine coronary arterioles

OBJECTIVE

Test the hypothesis that exercise training increases the contribution of BK(Ca) channels to endothelium-mediated dilation in coronary arterioles from collateral-dependent myocardial regions of chronically occluded pig hearts and may function downstream of H2O2.

METHODS

An ameroid constrictor was placed around the proximal left circumflex coronary artery to induce gradual occlusion in Yucatan miniature swine. Eight weeks postoperatively, pigs were randomly assigned to sedentary or exercise training (treadmill; 14 week) regimens.

RESULTS

Exercise training significantly enhanced bradykinin-mediated dilation in collateral-dependent arterioles (~125 μm diameter) compared with sedentary pigs. The BK(Ca) -channel blocker, iberiotoxin alone or in combination with the H2O2 scavenger, polyethylene glycol catalase, reversed exercise training-enhanced dilation in collateral-dependent arterioles. Iberiotoxin-sensitive whole-cell K+ currents (i.e., BK(Ca)-channel currents) were not different between smooth muscle cells of nonoccluded and collateral-dependent arterioles of sedentary and exercise trained groups.

CONCLUSIONS

These data provide evidence that BK(Ca)-channel activity contributes to exercise training-enhanced endothelium-dependent dilation in collateral-dependent coronary arterioles despite no change in smooth muscle BK(Ca)-channel current. Taken together, our findings suggest that a component of the bradykinin signaling pathway, which stimulates BK(Ca) channels, is enhanced by exercise training in collateral-dependent arterioles and suggest a potential role for H2O2 as the mediator.

Swimming and the heart

Exercise training is accepted to be beneficial in lowering morbidity and mortality in patients with cardiac disease. Swimming is a popular recreational activity, gaining recognition as an effective option in maintaining and improving cardiovascular fitness. Swimming is a unique form of exercise, differing from land-based exercises such as running in many aspects including medium, position, breathing pattern, and the muscle groups used. Water immersion places compressive forces on the body with resulting physiologic effects. We reviewed the physiologic effects and cardiovascular responses to swimming, the cardiac adaptations to swim training, swimming as a cardiac disease risk factor modifier, and the effects of swimming in those with cardiac disease conditions such as coronary artery disease, congestive heart failure and the long-QT syndrome.

Exercise training prior to myocardial infarction attenuates cardiac deterioration and cardiomyocyte dysfunction in rats

OBJECTIVES

The present study was performed to investigate 1) whether aerobic exercise training prior to myocardial infarction would prevent cardiac dysfunction and structural deterioration and 2) whether the potential cardiac benefits of aerobic exercise training would be associated with preserved morphological and contractile properties of cardiomyocytes in post-infarct remodeled myocardium.

METHODS

Male Wistar rats underwent an aerobic exercise training protocol for eight weeks. The rats were then assigned to sham surgery (SHAM), sedentary lifestyle and myocardial infarction or exercise training and myocardial infarction groups and were evaluated 15 days after the surgery. Left ventricular tissue was analyzed histologically, and the contractile function of isolated myocytes was measured. Student's t-test was used to analyze infarct size and ventricular wall thickness, and the other parameters were analyzed by the Kruskal-Wallis test followed by Dunn's test or a one-way analysis of variance followed by Tukey's test (p<0.05).

RESULTS

Myocardial infarctions in exercise-trained animals resulted in a smaller myocardial infarction extension, a thicker infarcted wall and less collagen accumulation as compared to myocardial infarctions in sedentary animals. Myocardial infarction-induced left ventricular dilation and cardiac dysfunction, as evaluated by +dP/dt and -dP/dt, were both prevented by previous aerobic exercise training. Moreover, aerobic exercise training preserved cardiac myocyte shortening, improved the maximum shortening and relengthening velocities in infarcted hearts and enhanced responsiveness to calcium.

CONCLUSION

Previous aerobic exercise training attenuated the cardiac dysfunction and structural deterioration promoted by myocardial infarction, and such benefits were associated with preserved cardiomyocyte morphological and contractile properties.

Diabetes, perioperative ischaemia and volatile anaesthetics: consequences of derangements in myocardial substrate metabolism

Volatile anaesthetics exert protective effects on the heart against perioperative ischaemic injury. However, there is growing evidence that these cardioprotective properties are reduced in case of type 2 diabetes mellitus. A strong predictor of postoperative cardiac function is myocardial substrate metabolism. In the type 2 diabetic heart, substrate metabolism is shifted from glucose utilisation to fatty acid oxidation, resulting in metabolic inflexibility and cardiac dysfunction. The ischaemic heart also loses its metabolic flexibility and can switch to glucose or fatty acid oxidation as its preferential state, which may deteriorate cardiac function even further in case of type 2 diabetes mellitus.Recent experimental studies suggest that the cardioprotective properties of volatile anaesthetics partly rely on changing myocardial substrate metabolism. Interventions that target at restoration of metabolic derangements, like lifestyle and pharmacological interventions, may therefore be an interesting candidate to reduce perioperative complications. This review will focus on the current knowledge regarding myocardial substrate metabolism during volatile anaesthesia in the obese and type 2 diabetic heart during perioperative ischaemia.

The effect of creatine supplementation on myocardial function, mitochondrial respiration and susceptibility to ischaemia/reperfusion injury in sedentary and exercised rats

AIM

To investigate the effects of dietary creatine supplementation alone and in combination with exercise on basal cardiac function, susceptibility to ischaemia/reperfusion injury and mitochondrial oxidative function. There has been an increase in the use of creatine supplementation among sports enthusiasts, and by clinicians as a therapeutic agent in muscular and neurological diseases. The effects of creatine have been studied extensively in skeletal muscle, but not in the myocardium.

METHODS

Male Wistar rats were swim-trained for 8 weeks, 5 days per week. Hearts were excised and either freeze-clamped for biochemical analysis or perfused on the isolated heart perfusion system to assess function and ischaemia/reperfusion tolerance. Mechanical function was documented in working heart and retrograde mode. The left coronary artery was ligated and infarct size determined. Mitochondrial oxidative capacity was quantified.

RESULTS

Aortic output recovery of hearts from the sedentary controls (CSed) was significantly higher than those from creatine-supplemented sedentary (CrSed), creatine-supplemented exercised (CrEx) as well as control exercised (CEx) groups. Ischaemic contracture of hearts from CrEx was significantly higher than that of CSed. There were no differences in infarct size and mitochondrial oxygen consumption.

CONCLUSION

This study suggests that creatine supplementation has no effects on basal cardiac function but reduces myocardial tolerance to ischaemia in hearts from exercise-trained animals, by increasing the ischaemic contracture and decreasing reperfusion aortic output. Exercise training alone also significantly decreased aortic output recovery. However, the exact mechanisms for these adverse myocardial effects are unknown and need further investigation.

Phosphoinositide 3-Kinase p110α Is a Master Regulator of Exercise-Induced Cardioprotection and PI3K Gene Therapy Rescues Cardiac Dysfunction

Background—

Numerous molecular and biochemical changes have been linked with the cardioprotective effects of exercise, including increases in antioxidant enzymes, heat shock proteins, and regulators of cardiac myocyte proliferation. However, a master regulator of exercise-induced protection has yet to be identified. Here, we assess whether phosphoinositide 3-kinase (PI3K) p110α is essential for mediating exercise-induced cardioprotection, and if so, whether its activation independent of exercise can restore function of the failing heart.

Methods and Results—

Cardiac-specific transgenic (Tg) mice with elevated or reduced PI3K(p110α) activity (constitutively active PI3K [caPI3K] and dominant negative PI3K, respectively) and non-Tg controls were subjected to 4 weeks of exercise training followed by 1 week of pressure overload (aortic-banding) to induce pathological remodeling. Aortic-banding in untrained non-Tg controls led to pathological cardiac hypertrophy, depressed systolic function, and lung congestion. This phenotype was attenuated in non-Tg controls that had undergone exercise before aortic-banding. Banded caPI3K mice were protected from pathological remodeling independent of exercise status, whereas exercise provided no protection in banded dominant negative PI3K mice, suggesting that PI3K is necessary for exercise-induced cardioprotection. Tg overexpression of heat shock protein 70 could not rescue the phenotype of banded dominant negative PI3K mice, and deletion of heat shock protein 70 from banded caPI3K mice had no effect. Next, we used a gene therapy approach (recombinant adeno-associated viral vector 6) to deliver caPI3K expression cassettes to hearts of mice with established cardiac dysfunction caused by aortic-banding. Mice treated with recombinant adeno-associated viral 6-caPI3K vectors had improved heart function after 10 weeks.

Conclusions—

PI3K(p110α) is essential for exercise-induced cardioprotection and delivery of caPI3K vector can improve function of the failing heart.

Akt1-mediated skeletal muscle growth attenuates cardiac dysfunction and remodeling after experimental myocardial infarction

BACKGROUND

It is appreciated that aerobic endurance exercise can attenuate unfavorable myocardial remodeling following myocardial infarction. In contrast, little is known about the effects of increasing skeletal muscle mass, typically achieved through resistance training, on this process. Here, we utilized transgenic (TG) mice that can induce the growth of functional skeletal muscle by switching Akt1 signaling in muscle fibers to assess the impact of glycolytic muscle growth on post-myocardial infarction cardiac remodeling.

METHODS AND RESULTS

Male-noninduced TG mice and their nontransgenic littermates (control) were subjected to left anterior coronary artery ligation. Two days after surgery, mice were provided doxycycline in their drinking water to activate Akt1 transgene expression in a skeletal muscle-specific manner. Myogenic Akt1 activation led to diminished left ventricular dilation and reduced contractile dysfunction compared with control mice. Improved cardiac function in Akt1 TG mice was coupled to diminished myocyte hypertrophy, decreased interstitial fibrosis, and increased capillary density. ELISA and protein array analyses demonstrated that serum levels of proangiogenic growth factors were upregulated in Akt1 TG mice compared with control mice. Cardiac eNOS was activated in Akt1 TG mice after myocardial infarction. The protective effect of skeletal muscle Akt activation on cardiac remodeling and systolic function was abolished by treatment with the eNOS inhibitor l-NAME.

CONCLUSIONS

Akt1-mediated skeletal muscle growth attenuates cardiac remodeling after myocardial infarction and is associated with an increased capillary density in the heart. This improvement appears to be mediated by skeletal muscle to cardiac communication, leading to activation of eNOS-signaling in the heart.

Exercise-induced cardiac preconditioning: how exercise protects your achy-breaky heart

The ability of exercise to protect the heart against ischemia-reperfusion (I/R) injury is well known in both human epidemiological studies and experimental animal models. In this review article, we describe what is currently known about the ability of exercise to precondition the heart against infarction. Just 1 day of exercise can protect the heart against ischemia/reperfusion damage, and this protection is upheld with months of exercise, making exercise one of the few sustainable preconditioning stimuli. Exercise preconditioning depends on the model and intensity of exercise, and appears to involve heightened oxidant buffering capacity, upregulated subunits of sarcolemmal ATP-sensitive potassium channels, and adaptations to cardiac mitochondria. We review the putative mechanisms involved in exercise preconditioning and point out many areas where future research is necessary to advance our understanding of how this stimulus confers resistance against I/R damage.

Conditional transgenic expression of fibroblast growth factor 9 in the adult mouse heart reduces heart failure mortality after myocardial infarction

BACKGROUND

Fibroblast growth factor 9 (FGF9) is secreted from bone marrow cells, which have been shown to improve systolic function after myocardial infarction (MI) in a clinical trial. FGF9 promotes cardiac vascularization during embryonic development but is only weakly expressed in the adult heart.

METHODS AND RESULTS

We used a tetracycline-responsive binary transgene system based on the α-myosin heavy chain promoter to test whether conditional expression of FGF9 in the adult myocardium supports adaptation after MI. In sham-operated mice, transgenic FGF9 stimulated left ventricular hypertrophy with microvessel expansion and preserved systolic and diastolic function. After coronary artery ligation, transgenic FGF9 enhanced hypertrophy of the noninfarcted left ventricular myocardium with increased microvessel density, reduced interstitial fibrosis, attenuated fetal gene expression, and improved systolic function. Heart failure mortality after MI was markedly reduced by transgenic FGF9, whereas rupture rates were not affected. Adenoviral FGF9 gene transfer after MI similarly promoted left ventricular hypertrophy with improved systolic function and reduced heart failure mortality. Mechanistically, FGF9 stimulated proliferation and network formation of endothelial cells but induced no direct hypertrophic effects in neonatal or adult rat cardiomyocytes in vitro. FGF9-stimulated endothelial cell supernatants, however, induced cardiomyocyte hypertrophy via paracrine release of bone morphogenetic protein 6. In accord with this observation, expression of bone morphogenetic protein 6 and phosphorylation of its downstream targets SMAD1/5 were increased in the myocardium of FGF9 transgenic mice.

CONCLUSIONS

Conditional expression of FGF9 promotes myocardial vascularization and hypertrophy with enhanced systolic function and reduced heart failure mortality after MI. These observations suggest a previously unrecognized therapeutic potential for FGF9 after MI.

Cardioprotection conferred by exercise training is blunted by blockade of the opioid system

OBJECTIVES

To investigate the effect of opioid receptor blockade on the myocardial protection conferred by chronic exercise and to compare exercise training with different strategies of myocardial protection (opioid infusion and brief periods of ischemia-reperfusion) preceding irreversible left anterior descending coronary ligation.

INTRODUCTION

The acute cardioprotective effects of exercise training are at least partly mediated through opioid receptor-dependent mechanisms in ischemia-reperfusion models.

METHODS

Male Wistar rats (n = 76) were randomly assigned to 7 groups: (1) control; (2) exercise training; (3) morphine; (4) intermittent ischemia-reperfusion (three alternating periods of left anterior descending coronary occlusion and reperfusion); (5) exercise training+morphine; (6) naloxone (a non-selective opioid receptor blocker) plus morphine; (7) naloxone before each exercise-training session. Myocardial infarction was established in all groups by left anterior descending coronary ligation. Exercise training was performed on a treadmill for 60 minutes, 5 times/week, for 12 weeks, at 60% peak oxygen (peak VO₂). Infarct size was histologically evaluated.

RESULTS

Exercise training significantly increased exercise capacity and ΔVO2 (VO₂ peak - VO₂ rest) (p < 0.01 vs. sedentary groups). Compared with control, all treatment groups except morphine plus naloxone and exercise training plus naloxone showed a smaller infarcted area (p < 0.05). No additional decrease in infarct size occurred in the exercise training plus morphine group. No difference in myocardial capillary density (p = 0.88) was observed in any group.

CONCLUSIONS

Exercise training, morphine, exercise training plus morphine and ischemia-reperfusion groups had a smaller infarcted area than the control group. The effect of chronic exercise training in decreasing infarct size seems to occur, at least in part, through the opioid receptor stimulus and not by increasing myocardial perfusion.

Prior exercise training does not prevent acute cardiac alterations after myocardial infarction in female rats

OBJECTIVE

This study aimed to investigate whether previous exercise training could prevent or attenuate acute cardiac alterations after myocardial infarction.

METHODS

Female rats were submitted to swim training (1 h/day; 5 days/week) or allowed to remain sedentary for 8 weeks. Afterwards, they were randomly assigned to left coronary artery occlusion or sham surgery. After this procedure, the rats remained sedentary for one week until euthanasia. Cardiac structural and functional analyses were performed using Doppler echocardiography. The rats that had a moderate or large infarct size were included in the evaluations. The data (mean ± SEM) were analyzed using a two-way ANOVA model followed by Tukey's post-hoc test.

RESULTS

After the surgery, no significant difference between the exercise and sedentary groups was observed in the left ventricular infarct sizes (34.58 ± 3.04 vs. 37.59 ± 3.07). In another group of rats evaluated with Evans blue 1 h after myocardial infarction, no siginificant difference in the area at risk was observed between the exercised and sedentary rats (49.73 ± 1.52 vs. 45.48 ± 3.49). The changes in the left ventricular fractional areas for the exercised and sedentary myocardial infarction groups (36 ± 2% and 39 ± 3%, respectively) were smaller than those for the exercise sham surgery (ES, 67 ± 1%) and sedentary sham surgery (SS, 69 ± 2%) groups. The E/A was higher in the sedentary myocardial infarction (4.4 ± 0.3) and exercised myocardial infarction (5.5 ± 0.3) rats than in the SS (2.4 ± 0.1) and ES (2.2 ± 0.1) rats.

CONCLUSION

Previous swim training of female rats does not attenuate systolic and diastolic function alterations after myocardial infarction induced by left coronary artery occlusion, suggesting that cardioprotection cannot be provided by exercise training in this experimental model.

Moderate exercise training provides left ventricular tolerance to acute pressure overload

The present study evaluated the impact of moderate exercise training on the cardiac tolerance to acute pressure overload. Male Wistar rats were randomly submitted to exercise training or sedentary lifestyle for 14 wk. At the end of this period, the animals were anaesthetized, mechanically ventilated, and submitted to hemodynamic evaluation with biventricular tip pressure manometers. Acute pressure overload was induced by banding the descending aorta to induce a 60% increase of peak systolic left ventricular pressure during 120 min. This resulted in the following experimental groups: 1) sedentary without banding (SED + Sham), 2) sedentary with banding (SED + Band), and 3) exercise trained with banding (EX + Band). In response to aortic banding, SED + Band animals could not sustain the 60% increase of peak systolic pressure for 120 min, even with additional narrowing of the banding. This was accompanied by a reduction of dP/dt(max) and dP/dt(min) and a prolongation of the time constant tau, indicating impaired systolic and diastolic function. This impairment was not observed in EX + Band (P < 0.05 vs. SED + Band). Additionally, compared with SED + Band, EX + Band presented less myocardial damage, exhibited attenuated protein expression of active caspase-3 and NF-κB (P < 0.016), and showed less protein carbonylation and nitration (P < 0.05). These findings support our hypothesis that exercise training has a protective role in the modulation of the early cardiac response to pressure overload.

Cardioprotective effects of nitrite during exercise

Exercise training has been shown to reduce many risk factors related to cardiovascular disease, including high blood pressure, high cholesterol, obesity, and insulin resistance. More importantly, exercise training has been consistently shown to confer sustainable protection against myocardial infarction in animal models and has been associated with improved survival following a heart attack in humans. It is still unclear how exercise training is able to protect the heart, but some studies have suggested that it increases a number of classical signalling molecules. For instance, exercise can increase components of the endogenous antioxidant defences (i.e. superoxide dismutase and catalase), increase the expression of heat shock proteins, activate ATP-sensitive potassium (K(ATP)) channels, and increase the expression and activity of endothelial nitric oxide (NO) synthase resulting in an increase in NO levels. This review article will provide a brief summary of the role that these signalling molecules play in mediating the cardioprotective effects of exercise. In particular, it will highlight the role that NO plays and introduce the idea that the stable NO metabolite, nitrite, may play a major role in mediating these cardioprotective effects.

Gene expression profile of rat left ventricles reveals persisting changes following chronic mild exercise protocol: implications for cardioprotection

Background

Epidemiological studies showed that physical exercise, specifically moderate lifelong training, is protective against cardiovascular morbidity and mortality. Most experimental work has focused into the effects and molecular mechanisms underlying intense, rather than mild exercise, by exploring the acute effect of training. Our study aims at investigating the cardioprotective effect of mild chronic exercise training and the gene expression profile changes at 48 hrs after the exercise cessation. Rats were trained at mild intensity on a treadmill: 25 m/min, 10%incline, 1 h/day, 3 days/week, 10 weeks; about 60% of the maximum aerobic power. By Affymetrix technology, we investigated the gene expression profile induced by exercise training in the left ventricle (LV) of trained (n = 10) and control (n = 10) rats. Cardioprotection was investigated by ischemia/reperfusion experiments (n = 10 trained vs. n = 10 control rats).

Results

Mild exercise did not induce cardiac hypertrophy and was cardioprotective as demonstrated by the decreased infarct size (p = 0.02) after ischemia/reperfusion experiments in trained with respect to control rats. Ten genes and 2 gene sets (two pathways) resulted altered in LV of exercised animals with respect to controls. We validated by real-time PCR the increased expression of four genes: similar to C11orf17 protein (RGD1306959), caveolin 3, enolase 3, and hypoxia inducible factor 1 alpha. Moreover, caveolin 3 protein levels were higher in exercised than control rats by immunohistochemistry and Western Blot analysis. Interestingly, the predicted gene similar to C11orf17 protein (RGD1306959) was significantly increased by exercise. This gene has a high homology with the human C11orf17 (alias: protein kinase-A interacting protein 1 or breast cancer associated gene 3). This is the first evidence that this gene is involved in the response to the exercise training.

Conclusion

Our data indicated that few, but significant, genes characterize the gene expression profile of the rat LV, when examined 48 hrs since the last training section and that mild exercise training determines cardioprotection without the induction of hypertrophy.

Prior exercise improves survival, infarct healing, and left ventricular function after myocardial infarction

We investigated the effects of voluntary wheel running before an acute myocardial infarction (MI) on survival, left ventricular (LV) remodeling and dysfunction and whether exercise before and after MI provides superior protection compared with either exercise intervention alone. After 2 wk of voluntary wheel running or sedentary housing, MI was induced in C57Bl/6 mice, after which exercise was stopped (EX-MI-SED and SED-MI-SED groups, where EX is exercise and SED is sedentary) or continued (EX-MI-EX and SED-MI-EX groups) for a period of 8 wk. Exercise after MI in SED-MI-EX mice had no effect on survival, the area of infarction, and global LV remodeling, but attenuated fibrosis and apoptosis in the remote myocardium and blunted LV dysfunction and pulmonary congestion compared with SED-MI-SED mice. Exercise before MI in both EX-MI-SED and EX-MI-EX mice decreased post-MI mortality compared with both SED-MI-SED and SED-MI-EX mice. Furthermore, in both pre-MI exercise groups, the infarct area was thicker, whereas interstitial fibrosis and apoptosis in the remote LV myocardium were blunted. In contrast, the ameliorating effects of either pre-MI or post-MI exercise alone on LV dysfunction were lost in EX-MI-EX mice, which may in part be related to the increased daily exercise distance in the first week post-MI in EX-MI-EX versus SED-MI-EX mice. In conclusion, exercise before or after MI blunted LV dysfunction, whereas only exercise before MI improved survival. These findings suggest that even when regular physical activity fails to prevent an acute MI, it can still act to improve cardiac function and survival after MI.

Endurance swimming stimulates transepithelial calcium transport and alters the expression of genes related to calcium absorption in the intestine of rats

Endurance impact exercise, e.g., running, is known to enhance the intestinal calcium absorption. However, nonimpact exercise, e.g., swimming, is more appropriate for osteoporotic patients with cardiovascular diseases or disorders of bone and joint, but the effect of swimming on the intestinal calcium transport was unknown. This study, therefore, aimed to investigate the transepithelial calcium transport and the expression of related genes in the intestine of rats trained to swim nonstop 1 h/day, 5 days/wk for 2 wk. We found that endurance swimming stimulated calcium transport in the duodenum, proximal jejunum, and cecum, while decreasing that in the proximal colon. Swimming affected neither the transepithelial potential difference nor resistance. As demonstrated by real-time PCR, the small intestine, especially the duodenum, responded to swimming by upregulating a number of genes related to the transcellular calcium transport, i.e., TRPV5, TRPV6, calbindin-D9k, PMCA1b, and NCX1, and the paracellular calcium transport, i.e., ZO-1, ZO-2, ZO-3, cingulin, occludin, and claudins, as well as nuclear receptor of 1,25(OH)2D3. In contrast, swimming downregulated those genes in the colon. Microarray analysis showed that swimming also altered the expression of duodenal genes related to the transport of several ions and nutrients, e.g., Na+, K+, Cl-, glucose, and amino acids. In conclusion, endurance swimming enhanced intestinal calcium absorption, in part, by upregulating the calcium transporter genes. The present microarray study also provided relevant information for further investigations into the intestinal nutrient and electrolyte transport during nonimpact exercise.

The protective effects of exercise and phosphoinositide 3-kinase (p110α) in the failing heart

Despite the development of a wide range of therapies, heart failure remains a leading cause of death in Western society. New therapies are needed to help combat this debilitating condition. Exercise is becoming an increasingly important feature of rehabilitation programmes for patients with heart failure. Before the 1980s, patients with heart failure were advised not to exercise as it was thought that exercise would increase the risk of a cardiac event (such as myocardial infarction). However, in recent years both aerobic and resistance training have been shown to be safe and beneficial for patients with heart failure, improving exercise tolerance and quality of life, and preventing muscular deconditioning. The molecular mechanisms responsible for exercise-induced cardioprotection are yet to be elucidated, however studies in transgenic mice have identified PI3K(p110α) (phosphoinositide 3-kinase p110α) as a likely mediator. PI3K(p110α) is a lipid kinase which is activated in the heart during chronic exercise training, and is important for maintaining heart structure and function in various pathological settings. In the present review the protective effects of PI3K(p110α) in the failing heart and its potential as a therapeutic strategy for the treatment of heart failure is discussed.

Exercise training delays cardiac dysfunction and prevents calcium handling abnormalities in sympathetic hyperactivity-induced heart failure mice

Exercise training (ET) is a coadjuvant therapy in preventive cardiology. It delays cardiac dysfunction and exercise intolerance in heart failure (HF); however, the molecular mechanisms underlying its cardioprotection are poorly understood. We tested the hypothesis that ET would prevent Ca2+ handling abnormalities and ventricular dysfunction in sympathetic hyperactivity-induced HF mice. A cohort of male wild-type (WT) and congenic α2A/α2C-adrenoceptor knockout (α2A/α2CARKO) mice with C57BL6/J genetic background (3–5 mo of age) were randomly assigned into untrained and exercise-trained groups. ET consisted of 8-wk swimming session, 60 min, 5 days/wk. Fractional shortening (FS) was assessed by two-dimensional guided M-mode echocardiography. The protein expression of ryanodine receptor (RyR), phospho-Ser2809-RyR, sarcoplasmic reticulum Ca2+ ATPase (SERCA2), Na+/Ca2+ exchanger (NCX), phospholamban (PLN), phospho-Ser16-PLN, and phospho-Thr17-PLN were analyzed by Western blotting. At 3 mo of age, no significant difference in FS and exercise tolerance was observed between WT and α2A/α2CARKO mice. At 5 mo, when cardiac dysfunction is associated with lung edema and increased plasma norepinephrine levels, α2A/α2CARKO mice presented reduced FS paralleled by decreased SERCA2 (26%) and NCX (34%). Conversely, α2A/α2CARKO mice displayed increased phospho-Ser16-PLN (76%) and phospho-Ser2809-RyR (49%). ET in α2A/α2CARKO mice prevented exercise intolerance, ventricular dysfunction, and decreased plasma norepinephrine. ET significantly increased the expression of SERCA2 (58%) and phospho-Ser16-PLN (30%) while it restored the expression of phospho-Ser2809-RyR to WT levels. Collectively, we provide evidence that improved net balance of Ca2+ handling proteins paralleled by a decreased sympathetic activity on ET are, at least in part, compensatory mechanisms against deteriorating ventricular function in HF.

Myocardial protection in man--from research concept to clinical practice

Myocardial protection aims at preventing myocardial tissue loss: (a) In the acute stage, i.e., during primary angioplasty in acute myocardial infarction. In this setup, the attenuation of reperfusion injury is the main target. As a "mechanical" means, post-conditioning has already been tried in man with encouraging results. Pharmacologic interventions that could be of promise are statins, insulin, peptide hormones, including erythropoietin, fibroblast growth factor, and many others. (b) The patient with chronic coronary artery disease offers another paradigm, with the target of avoidance of further myocyte loss through apoptosis and inflammation. Various pharmacologic agents may prove useful in this context, together with exercise and "mechanical" improvement of cardiac function with attenuation of myocardial stretch, which by itself is a noxious influence. A continuous effort toward acute and chronically preserving myocardial integrity is a concept concerning both the researcher and the clinician.