Exercise-induced cardioprotection--biochemical, morphological and functional evidence in whole tissue and isolated mitochondria

Lifelong exercise training modulates cardiac mitochondrial phosphoproteome in rats

Moderate physical activity has traditionally been associated with the improvement of cardiac function and, consequently, with the extension of life span. Mitochondria play a key role in the adaptation of heart muscle to exercise-related metabolic demands. In order to disclose the molecular mechanisms underlying the beneficial effect of lifelong physical activity in cardiac function, we performed label-free quantitative mass spectrometry-based proteomics of Sprague-Dawley rat heart mitochondrial proteome and phosphoproteome. Our data revealed that 54 weeks of moderate treadmill exercise modulates the abundance of proteins involved in the generation of precursor metabolites and cellular respiration, suggesting an increase in carbohydrate oxidation-based metabolism. Moreover, from the 1335 phosphopeptides identified in this study, 6 phosphosites were exclusively assigned to heart mitochondria from sedentary rats and 17 to exercised animals, corresponding to 6 and 16 proteins, respectively. Most proteins exhibiting significant alterations in specific phosphorylation sites were involved in metabolism. Analysis of the acquired data led to the identification of several kinases potentially modulated by exercise training, which were selected for further validation. Indeed, higher protein abundance levels of RAF and p38 in mitochondria were confirmed to be modulated by sustained exercise. Our work describes the plasticity of heart mitochondria in response to long exercise programs manifested by the reprogramming of phosphoproteome and provides evidence for the kinases involved in the regulation of metabolic pathways and mitochondrial maintenance.

Exercise training boosts eNOS-dependent mitochondrial biogenesis in mouse heart: role in adaptation of glucose metabolism

Endurance exercise training increases cardiac energy metabolism through poorly understood mechanisms. Nitric oxide (NO) produced by endothelial NO synthase (eNOS) in cardiomyocytes contributes to cardiac adaptation. Here we demonstrate that the NO donor diethylenetriamine-NO (DETA-NO) activated mitochondrial biogenesis and function, as assessed by upregulated peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear respiratory factor 1, and mitochondrial transcription factor A (Tfam) expression, and by increased mitochondrial DNA content and citrate synthase activity in primary mouse cardiomyocytes. DETA-NO also induced mitochondrial biogenesis and function and enhanced both basal and insulin-stimulated glucose uptake in HL-1 cardiomyocytes. The DETA-NO-mediated effects were suppressed by either PGC-1α or Tfam small-interference RNA in HL-1 cardiomyocytes. Wild-type and eNOS(-/-) mice were subjected to 6 wk graduated swim training. We found that eNOS expression, mitochondrial biogenesis, mitochondrial volume density and number, and both basal and insulin-stimulated glucose uptake were increased in left ventricles of swim-trained wild-type mice. On the contrary, the genetic deletion of eNOS prevented all these adaptive phenomena. Our findings demonstrate that exercise training promotes eNOS-dependent mitochondrial biogenesis in heart, which behaves as an essential step in cardiac glucose transport.

Modulation of cardiac mitochondrial permeability transition and apoptotic signaling by endurance training and intermittent hypobaric hypoxia

BACKGROUND

Modulation of the mitochondrial permeability transition pore (MPTP) and inhibition of the apoptotic signaling are critically associated with the cardioprotective phenotypes afforded by both intermittent hypobaric-hypoxia (IHH) and endurance-training (ET). We recently proposed that IHH and ET improve cardiac function and basic mitochondrial capacity, although without showing addictive effects. Here we investigate whether a combination of IHH and ET alters cardiac mitochondrial vulnerability to MPTP and related apoptotic signaling.

METHODS

Male Wistar rats were divided into normoxic-sedentary (NS), normoxic-exercised (NE, 1h/day/5 week treadmill-running), hypoxic-sedentary (HS, 6000 m, 5h/day/5 weeks) and hypoxic-exercised (HE) to study susceptibility to calcium-induced cardiac MPTP opening. Mitochondrial cyclophilin D (CypD), adenine nucleotide translocator (ANT), Bax and Bcl-2 protein contents were semi-quantified by Western blotting. Cardiac caspase 3-, 8- and 9-like activities were measured. Mitochondrial aconitase and superoxide dismutase (MnSOD) activity and malondialdehyde (MDA) and sulphydryl group (-SH) content were determined.

RESULTS

Susceptibility to MPTP decreased in NE and HS vs. NS and even further in HE. The ANT content increased in HE vs. NS. Bcl-2/Bax ratio increased in NE and HS compared to NS. Decreased activities in tissue caspase 3-like (HE vs. NS) and caspase 9-like (HS and HE vs. NS) were observed. Mitochondrial aconitase increased in NE and HS vs. NS. No alterations between groups were observed for caspase 8-like activity, MnSOD, CypD, MDA and -SH.

CONCLUSIONS

Data confirm that IHH and ET modulate cardiac mitochondria to a protective phenotype characterized by decreased MPTP induction and apoptotic signaling, although without visible addictive effects as initially hypothesized.

Do we age because we have mitochondria?

The process of aging remains a great riddle. Production of reactive oxygen species (ROS) by mitochondria is an inevitable by-product of respiration, which has led to a hypothesis proposing the oxidative impairment of mitochondrial components (e.g., mtDNA, proteins, lipids) that initiates a vicious cycle of dysfunctional respiratory complexes producing more ROS, which again impairs function. This does not exclude other processes acting in parallel or targets for ROS action in other organelles than mitochondria. Given that aging is defined as the process leading to death, the role of mitochondria-based impairments in those organ systems responsible for human death (e.g., the cardiovascular system, cerebral dysfunction, and cancer) is described within the context of "garbage" accumulation and increasing insulin resistance, type 2 diabetes, and glycation of proteins. Mitochondrial mass, fusion, and fission are important factors in coping with impaired function. Both biogenesis of mitochondria and their degradation are important regulatory mechanisms stimulated by physical exercise and contribute to healthy aging. The hypothesis of mitochondria-related aging should be revised to account for the limitations of the degradative capacity of the lysosomal system. The processes involved in mitochondria-based impairments are very similar across a large range of organisms. Therefore, studies on model organisms from yeast, fungi, nematodes, flies to vertebrates, and from cells to organisms also add considerably to the understanding of human aging.

Myocardial mitochondrial oxidative stress and dysfunction in intense exercise: regulatory effects of quercetin

INTRODUCTION

Oxidative stress plays a pivotal role in the intense exercise-induced myocardium injury, and mitochondrial compartment is presumed as the main source and susceptible target of intracellular reactive oxygen species (ROS).

PURPOSE

The objective of this study was to evaluate the protective effect of quercetin, a naturally occurring flavonoids possessing antioxidant effect on repeated intense exercise-induced mitochondrial oxidative stress and dysfunction.

METHODS

Adult male BALB/C mice were treated by quercetin (100 mg/kg bw) for 4 weeks and subjected to the exercise protocol on a treadmill (28 m/min at 5° slope for 90 min) for seven consecutive days concurrently at the fourth week.

RESULTS

Intense exercise in mice resulted in the leakage of creatine kinase-MB (increased from 221.5 ± 33.8 to 151.1 ± 19.1 U/l, P < 0.01) and ultrastructural malformation mainly evidenced by disrupted myofibrils and swollen mitochondria, which was overtly attenuated by quercetin prophylaxis. Quercetin pretreatment evidently alleviated mitochondrial oxidative stress by inhibiting glutathione depletion and aconitase inactivation, ROS over-generation, and lipid peroxidation in cardiac mitochondria of intense exercise mice. Furthermore, mitochondrial dysfunction manifested by decreased mitochondrial membrane potential (68.6 ± 7.6 versus 100.0 ± 7.7 %, P < 0.01) and respiratory control ratio (5.03 ± 0.55 versus 7.48 ± 0.71, P < 0.01) induced as a consequence of acute exercise was markedly mitigated by quercetin precondition.

CONCLUSION

Quercetin protects mouse myocardium against intense exercise injury, especially ultrastructural damage and mitochondrial dysfunction, probably through its beneficial antioxidative effect, highlighting a promising strategy for over-training injury by naturally occurring phytochemicals.

Exercise as a therapeutic tool to prevent mitochondrial degeneration in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease, encompassing hepatic steatosis, nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis, is a significant health problem associated with modern lifestyle, based on caloric overconsumption and physical inactivity. Although the mechanisms associated with progression from the 'benign' steatosis to NASH are still elusive, mitochondrial dysfunction seems to play an important role in this degenerative process. Degeneration of mitochondrial function during NASH has been associated with impaired β-oxidation, oxidative phosphorylation and increased reactive oxygen species production, contributing to hepatocyte death and inflammatory response. Despite the fact that several therapeutic approaches can be used in the context of NASH, including insulin-sensitizing agents, anti-obesity drugs, lipid-lowering drugs or mitochondrial-targeted drugs, dietary and physical activity are still the most effective strategies. In fact, active lifestyles decrease insulin resistance and body weight and result in decreased histological signs of liver injury. In fatty liver, physical activity prevents the disease progression through mitochondrial adaptations, namely by increasing cytochrome c content, enzyme activities and fatty acid oxidation, which are lost after some days of physical inactivity. However, less is known about the effect of physical activity on NASH-associated mitochondrial dysfunction. After a brief characterization of NASH and its association with liver mitochondrial (dys)function, the present review addresses the impact of physical (in)activity on NASH and, particularly, the possible contribution of active lifestyles to the modulation of liver mitochondrial dysfunction.

Synergistic impact of endurance training and intermittent hypobaric hypoxia on cardiac function and mitochondrial energetic and signaling

BACKGROUND

Intermittent hypobaric-hypoxia (IHH) and endurance-training (ET) are cardioprotective strategies against stress-stimuli. Mitochondrial modulation appears to be an important step of the process. This study aimed to analyze whether a combination of these approaches provides additive or synergistic effects improving heart-mitochondrial and cardiac-function.

METHODS

Two-sets of rats were divided into normoxic-sedentary (NS), normoxic-exercised (NE, 1 h/day/5 weeks treadmill-running), hypoxic-sedentary (HS, 6000 m, 5h/day/5 weeks) and hypoxic-exercised (HE) to study overall cardiac and mitochondrial function. In vitro cardiac mitochondrial oxygen consumption and transmembrane potential were evaluated. OXPHOS subunits and ANT protein content were semi-quantified by Western blotting. HIF-1α, VEGF, VEGF-R1 VEGF-R2, BNP, SERCA2a and PLB expressions were measured by qRT-PCR and cardiac function was characterized by echocardiography and hemodynamic parameters.

RESULTS

Respiratory control ratio (RCR) increased in NE, HS and HE vs. NS. Susceptibility to anoxia/reoxygenation-induced dysfunction decreased in NE, HS and HE vs. NS. HS decreased mitochondrial complex-I and -II subunits; however HE completely reverted the decreased content in complex-II subunits. ANT increased in HE. HE presented normalized ventricular-arterial coupling (Ea) and BNP myocardial levels and significantly improved myocardial performance as evaluated by increased cardiac output and normalization of the Tei index vs.

HS CONCLUSION

Data demonstrates that IHH and ET confer cardiac mitochondria with a more resistant phenotype although without visible addictive effects at least under basal conditions. It is suggested that the combination of both strategies, although not additive, results into improved cardiac function.

Both aerobic exercise and resveratrol supplementation attenuate doxorubicin-induced cardiac injury in mice

Because doxorubicin (DOX)-containing chemotherapy causes left ventricular (LV) dysfunction and remodeling that can progress to heart failure, strategies to alleviate DOX cardiotoxicity are necessary to improve health outcomes of patients surviving cancer. Although clinical evidence suggests that aerobic exercise training (ET) can prevent cardiotoxicity in patients undergoing DOX chemotherapy, the physiological mechanisms involved have not been extensively studied, nor is it known whether compounds [such as resveratrol (RESV)] have similar beneficial effects. With the use of a murine model of chronic DOX exposure, this study compared the efficacy of modest ET to RESV treatment on exercise performance, LV remodeling, and oxidative stress resistance. Mice were divided into four groups that received saline, DOX (8 mg/kg ip, one time per week), DOX + RESV (4 g/kg diet, ad libitum), and DOX + ET (45 min of treadmill exercise, 5 days/wk) for 8 wk. LV function and morphology were evaluated by in vivo echocardiography. DOX caused adverse LV remodeling that was partially attenuated by modest ET and completely prevented by RESV. These effects were paralleled by improvements in exercise performance. The cardioprotective properties of ET and RESV were associated with reduced levels of atrial natriuretic peptide and the lipid peroxidation by-product, 4-hydroxy-2-nonenal. In addition, ET and RESV increased the expression of cardiac sarcoplasmic/endoplasmic reticulum calcium-ATPase 2a, superoxide dismutase, mitochondrial electron transport chain complexes, and mitofusin-1 and -2 in mice administered DOX. Compared with modest ET, RESV more effectively prevented DOX-induced LV remodeling and was associated with the reduction of DOX-induced oxidative stress. Our findings have important implications for protecting patients against DOX-associated cardiac injury.

Novel role for thioredoxin reductase-2 in mitochondrial redox adaptations to obesogenic diet and exercise in heart and skeletal muscle

Increased fatty acid availability and oxidative stress are physiological consequences of exercise (Ex) and a high-fat, high-sugar (HFHS) diet. Despite these similarities, the global effects of Ex are beneficial, whereas HFHS diets are largely deleterious to the cardiovascular system. The reasons for this disparity are multifactorial and incompletely understood. We hypothesized that differences in redox adaptations following HFHS diet in comparison to exercise may underlie this disparity, particularly in mitochondria. Our objective in this study was to determine mechanisms by which heart and skeletal muscle (red gastrocnemius, RG) mitochondria experience differential redox adaptations to 12 weeks of HFHS diet and/or exercise training (Ex) in rats. Surprisingly, both HFHS feeding and Ex led to contrasting effects in heart and RG, in that mitochondrial H2O2 decreased in heart but increased in RG following both HFHS diet and Ex, in comparison to sedentary animals fed a control diet. These differences were determined to be due largely to increased antioxidant/anti-inflammatory enzymes in the heart following the HFHS diet, which did not occur in RG. Specifically, upregulation of mitochondrial thioredoxin reductase-2 occurred with both HFHS and Ex in the heart, but only with Ex in RG, and systematic evaluation of this enzyme revealed that it is critical for suppressing mitochondrial H2O2 during fatty acid oxidation. These findings are novel and important in that they illustrate the unique ability of the heart to adapt to oxidative stress imposed by HFHS diet, in part through upregulation of thioredoxin reductase-2. Furthermore, upregulation of thioredoxin reductase-2 plays a critical role in preserving the mitochondrial redox status in the heart and skeletal muscle with exercise.

Role of four-week resistance exercise in preserving the heart against ischaemia-reperfusion-induced injury

Objective

We studied the cardioprotective effect of resistance training against ischaemia–reperfusion-induced injury.

Methods

Forty male rats were divided into trained and sedentary groups (n = 20 for each). The trained rats were exercised at 12 repetitions/set, four sets/day and five days/week for four weeks. Transient regional ischaemia of the left anterior descending coronary artery (40 min) was followed by 80 min of reperfusion.

Results

Baseline developed and diastolic pressures and coronary flow were similar in the two groups. While diastolic pressure increased and developed pressure and coronary flow decreased in both the ischaemic and perfusion periods (as indices of cardiac damage), there were no statistically significant differences between the trained and sedentary groups in these parameters. Resistance training did not significantly change the infarct size and apoptosis rate.

Conclusion

We did not see a cardioprotective effect of resistance exercise against ischaemia–reperfusion-induced injury in this study. A precise conclusion about this issue needs more investigations.

Insulin Signaling, GSK-3, Heat Shock Proteins and the Natural History of Type 2 Diabetes Mellitus: A Hypothesis

Metabolic syndrome and type 2 diabetes are progressive, indolent, multi-organ diseases. Understanding the abnormalities of heat shock proteins (HSPs) in these diseases is paramount to understanding their pathogenesis. In insulin resistant states and diabetes, heat shock factor 1(HSF-1) is low in insulin sensitive tissues, resulting in low Hsp 60, 70, and 90 levels. We propose that low Hsps levels are the result of decreased insulin action leading to less phosphorylation of PI3K, PKB, and glycogen synthase kinase-3 (GSK-3). Importantly, less GSK-3 phosphorylation (and thus more GSK-3 activity) will lower HSF-1. Low Hsps make organs vulnerable to injury, impair the stress response, accelerate systemic inflammation, raise islet amyloid polypeptide, and increase insulin resistance. Feeding this cycle is excess saturated fat and calorie consumption, hypertension, inactivity, aging, and genetic predisposition- all of which are a associated with high GSK-3 activity and low Hsps. Support for the proposed "vicious" cycle is based on the observation that GSK-3 inhibition and Hsp stimulation result in increased insulin sensitivity, reduced accumulation of degenerative proteins with in the cell, improved wound healing, decreased organ damage and improved recovery from vascular ischemia. Recognizing GSK-3 and Hsps in the pathogenesis of insulin resistance, the central common feature of the metabolic syndrome, and type 2 diabetes will expand our understanding of the disease, offering new therapeutic options.

Inhibition of the Mitochondrial Permeability Transition for Cytoprotection: Direct versus Indirect Mechanisms

Mitochondria are fascinating organelles, which fulfill multiple cellular functions, as diverse as energy production, fatty acid β oxidation, reactive oxygen species (ROS) production and detoxification, and cell death regulation. The coordination of these functions relies on autonomous mitochondrial processes as well as on sustained cross-talk with other organelles and/or the cytosol. Therefore, this implies a tight regulation of mitochondrial functions to ensure cell homeostasis. In many diseases (e.g., cancer, cardiopathies, nonalcoholic fatty liver diseases, and neurodegenerative diseases), mitochondria can receive harmful signals, dysfunction and then, participate to pathogenesis. They can undergo either a decrease of their bioenergetic function or a process called mitochondrial permeability transition (MPT) that can coordinate cell death execution. Many studies present evidence that protection of mitochondria limits disease progression and severity. Here, we will review recent strategies to preserve mitochondrial functions via direct or indirect mechanisms of MPT inhibition. Thus, several mitochondrial proteins may be considered for cytoprotective-targeted therapies.

The Correlation Between Small Dense LDL and Reactive Oxygen Metabolites in a Physical Activity Intervention in Hyperlipidemic Subjects

Background

Small dense low-density lipoprotein (sdLDL), which has a small LDL particle size with a greater susceptibility to oxidation, is considered a risk marker for cardiovascular disease (CVD). The diacron reactive oxygen metabolites (d-ROMs) have recently been introduced as a clinically useful oxidative stress-related marker. Physical activity can reduce the CVD risk. The present study investigated the correlation between the changes of the mean LDL particle size and the oxidative stress status, as assessed by the d-ROMs, in a physical activity intervention in hyperlipidemic subjects.

Methods

We performed a 6-month intervention study of 30 hyperlipidemic subjects (12 male/18 female, mean age 64 years), focusing on a moderate physical activity increase. The clinical data, including the atherosclerotic risk factors besides the mean LDL particle size measured with the gel electrophoresis and the d-ROMs, were evaluated pre- and post-intervention.

Results

The mean LDL particle size was significantly larger in the post-intervention than in the pre-intervention evaluation (26.9 ± 0.3 (SD) vs. 27.1 ± 0.4 nm, P < 0.01), while the d-ROMs levels were significantly reduced in the post-intervention period compared to those at pre-intervention (319 ± 77 vs. 290 ± 73 U. Carr., P < 0.05). A stepwise multiple regression analysis revealed that there was an independent, significant and inverse correlation between the pre- and post-intervention changes of the d-ROMs and the mean LDL particle size (β = -0.55, P < 0.01).

Conclusions

The intervention study suggests that sdLDL and oxidative stress can concomitantly affect the risk of developing CVD and that both factors can improve by even a moderate increase in physical activity among hyperlipidemic subjects.

Voluntary running in mice beneficially modulates myocardial ischemic tolerance, signaling kinases, and gene expression patterns

Exercise triggers hormesis, conditioning hearts against damaging consequences of subsequent ischemia-reperfusion (I/R). We test whether “low-stress” voluntary activity modifies I/R tolerance and molecular determinants of cardiac survival. Male C57BL/6 mice were provided 7-day access to locked (7SED) or rotating (7EX) running-wheels before analysis of cardiac prosurvival (Akt, ERK 1/2) and prodeath (GSK3β) kinases, transcriptomic adaptations, and functional tolerance of isolated hearts to 25-min ischemia/45-min reperfusion. Over 7 days, 7EX mice increased running from 2.1 ± 0.2 to 5.3 ± 0.3 km/day (mean speed 38 ± 2 m/min), with activity improving myocardial I/R tolerance: 7SED hearts recovered 43 ± 3% of ventricular force with diastolic contracture of 33 ± 3 mmHg, whereas 7EX hearts recovered 63 ± 5% of force with diastolic dysfunction reduced to 23 ± 2 mmHg ( P < 0.05). Cytosolic expression (total protein) of Akt and GSK3β was unaltered, while ERK 1/2 increased 30% in 7EX vs. 7SED hearts. Phosphorylation of Akt and ERK 1/2 was unaltered, whereas GSK3β phosphorylation increased ∼90%. Microarray interrogation identified significant changes (≥1.3-fold expression change, ≤5% FDR) in 142 known genes, the majority (92%) repressed. Significantly modified paths/networks related to inflammatory/immune function (particularly interferon-dependent), together with cell movement, growth, and death. Of only 14 induced transcripts, 3 encoded interrelated sarcomeric proteins titin, α-actinin, and myomesin-2, while transcripts for protective actin-stabilizing ND1-L and activator of mitochondrial biogenesis ALAS1 were also induced. There was no transcriptional evidence of oxidative heat-shock or other canonical “stress” responses. These data demonstrate that relatively brief voluntary activity substantially improves cardiac ischemic tolerance, an effect independent of shifts in Akt, but associated with increased total ERK 1/2 and phospho-inhibition of GSK3β. Transcriptomic data implicate inflammatory/immune and sarcomeric modulation in activity-dependent protection.

Hypoxia-mediated prior induction of monocyte-expressed HSP72 and HSP32 provides protection to the disturbances to redox balance associated with human sub-maximal aerobic exercise

HSP72 is rapidly expressed in response to a variety of stressors in vitro and in vivo (including hypoxia). This project sought a hypoxic stimulus to elicit increases in HSP72 and HSP32 in attempts to confer protection to the sub-maximal aerobic exercise-induced disturbances to redox balance. Eight healthy recreationally active male subjects were exposed to five consecutive days of once-daily hypoxia (2,980 m, 75 min). Seven days prior to the hypoxic acclimation period, subjects performed 60 min of cycling on a cycle ergometer (exercise bout 1-EXB1), and this exercise bout was repeated 1 day post-cessation of the hypoxic period (exercise bout 2-EXB2). Blood samples were taken immediately pre- and post-exercise and 1, 4 and 8 h post-exercise for HSP72 and immediately pre, post and 1 h post-exercise for HSP32, TBARS and glutathione [reduced (GSH), oxidised (GSSG) and total (TGSH)], with additional blood samples obtained immediately pre-day 1 and post-day 5 of the hypoxic acclimation period for the same indices. Monocyte-expressed HSP32 and HSP72 were analysed by flow cytometry, with measures of oxidative stress accessed by commercially available kits. There were significant increases in HSP72 (P < 0.001), HSP32 (P = 0.03), GSSG (t = 9.5, P < 0.001) and TBARS (t = 5.6, P = 0.001) in response to the 5-day hypoxic intervention, whereas no significant changes were observed for GSH (P = 0.22) and TGSH (P = 0.25). Exercise-induced significant increases in HSP72 (P < 0.001) and HSP32 (P = 0.003) post-exercise in EXB1; this response was absent for HSP72 (P ≥ 0.79) and HSP32 (P ≥ 0.99) post-EXB2. The hypoxia-mediated increased bio-available HSP32 and HSP72 and favourable alterations in glutathione redox, prior to exercise commencing in EXB2 compared to EXB1, may acquiesce the disturbances to redox balance encountered during the second physiologically identical exercise bout.

Effects of different physical training protocols on ventricular oxidative stress parameters in infarction-induced rats

AIM

Physical exercise is important in the prevention and treatment of cardiovascular diseases. Nevertheless, controversy remains around type and intensity of effort required for significant biochemical protective changes. This study investigates two exercise protocols on ventricular oxidative parameters in rats post-infarction.

MAIN METHODS

Thirty-six 2-month-old male Wistar rats were divided in two groups (n=18): Sham and acute myocardial infarction (AMI) conducted by blocking the coronary artery. Thirty days after AMI, animals were divided in 6 subgroups (n=6): sham, sham+continuous training (60 min), sham+interval training, AMI, AMI+continuous training, and AMI+interval training. Training was conducted in water (30-32°C) 5 times a week for 6 weeks. Animals were sacrificed 48 h after the last exercise routine. Left ventricles were used for oxidative stress analyses (antioxidant enzyme activity and level, oxidative damage) and HIF1α and cit c oxidase expression.

KEY FINDINGS

After AMI, both exercise models decreased superoxide levels significantly. Training routines did not alter SOD expression and activity, though CAT expression increased with continuous training and GPX level diminished in both training groups, which coincided with the increase in GPX activity. Lipid damage decreased only in the continuous training group, while protein damage decreased only in the interval training group. Cytochrome C increased in both groups, while HIF-1 α dropped significantly after both exercise protocols.

SIGNIFICANCE

Significant improvement occurred in myocardium redox status in rats challenged with AMI after different training routines. However, continuous training seems to be more efficient in improving the parameters analyzed.

Amlodipine attenuates oxidative stress in the heart and blood of high-cholesterol diet rabbits

INTRODUCTION

Oxidative stress is a key component of atherosclerosis. It has been suggested that amlodipine inhibits oxidative stress. In this study, we evaluated the effects of amlodipine on the total antioxidant capacity of heart tissue and blood in 36 control and cholesterol-fed male New Zealand white rabbits.

METHODS

The rabbits were divided into four groups (n = 9). Group 1 rabbits were fed a regular diet, group 2 were fed a diet with 2% cholesterol, group 3 were fed a regular diet plus 5 mg/kg/day oral amlodipine, and group 4 were fed 2% cholesterol diet plus amlodipine 5 mg/kg/day. At the end of eight weeks, blood samples were drawn and at the same time heart tissue was isolated and frozen in liquid nitrogen. After homogenisation, the solution was centrifuged and the light supernatant was stored at -80°C. This was used for determination of glutathione peroxidase (GPX), superoxide dismutase (SOD) and (MDA) levels.

RESULTS

Eight weeks of amlodipine treatment significantly reduced the levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides in the group on the hypercholesterolaemic diet (p < 0.05). In the blood, the level of thiobarbituric acid-reactive substances increased in the rabbits on the 2% cholesterol diet (group 2) and 2% cholesterol-plusamlodipine diet (group 4) and decreased in the amlodipineonly group (group 3) (p < 0.05). Lipid peroxidation in the heart tissue was similar to that in the blood, except in the amlodipine-only group (group 3). In the blood, the activity of total SOD (tSOD) decreased in the group on the 2% cholesterol diet (group 2) (p < 0.05) and markedly increased in the amlodipine-only (group 3) and 2% cholesterol-plusamlodipine groups (group 4) (p < 0.05).

CONCLUSION

Amlodipine decreased oxidative stress in the heart and blood and improved the lipid profile in cholesterolfed rabbits. Therefore, it may be considered a useful tool for the reduction of oxidative stress and improvement of lipid profiles in diseases related to atherosclerosis.

Effect of short- and long-term strength exercise on cardiac oxidative stress and performance in rat

Increase in heart metabolism during severe exercise facilitates production of ROS and result in oxidative stress. Due to shortage of information, the effect of chronic strength exercise on oxidative stress and contractile function of the heart was assessed to explore the threshold for oxidative stress in this kind of exercise training. Male Wistar rats (80) were divided into two test groups exercised 1 and 3 months and two control groups without exercise. Strength exercise was carried by wearing a Canvas Jacket with weights and forced rats to lift the weights. Rats were exercised at 70% of maximum lifted weight 6 days/week, four times/day, and 12 repetitions each time. Finally, the hearts of ten rats/group were homogenized and MDA, SOD, GPX, and catalase (CAT) were determined by ELISA method. In other ten rats/group, left ventricle systolic and end diastolic pressures (LVSP and LVEDP) and contractility indices (LVDP and +dp/dt max) and relaxation velocity (-dp/dt max) were recorded. The coronary outflow was collected. Short- and long-term strength exercise increased heart weight and heart/BW ratio (P < 0.05). In the 3-month exercise group, basal heart rate decreased (P < 0.05). LVEDP did not change but LVDP, +dp/dt max, -dp/dt max, and coronary flow significantly increased in both exercise groups (P < 0.05). None of MDA or SOD, GPX, and CAT significantly changed. The results showed that sub-maximal chronic strength exercise improves heart efficiency without increase in oxidative stress index or decrease in antioxidant defense capacity. These imply that long-time strength exercise up to this intensity is safe for cardiac health.

Proteomic responses of skeletal and cardiac muscle to exercise

Regular exercise is effective in the prevention of chronic diseases and confers a lower risk of death in individuals displaying risk factors such as hypertension and dyslipidemia. Thus, knowledge of the molecular responses to exercise provides a valuable contrast for interpreting investigations of disease and can highlight novel therapeutic targets. While exercise is an everyday experience and can be conceptualized in simple terms, it is also a complex physiological phenomenon and investigation of exercise responses requires sophisticated analytical techniques and careful standardization of the exercise stimulus. Proteomic investigation of exercise is in its infancy but the ability to link changes in function with comprehensive changes in protein expression and post-translational modification holds great promise for advancing physiology. This article highlights recent pioneering work investigating the effects of exercise in skeletal and cardiac muscle that has uncovered novel mechanisms underlying the benefits of physical activity.

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.

Pathophysiology of myocardial reperfusion injury: preconditioning, postconditioning, and translational aspects of protective measures

Heart diseases due to myocardial ischemia, such as myocardial infarction or ischemic heart failure, are major causes of death in developed countries, and their number is unfortunately still growing. Preliminary exploration into the pathophysiology of ischemia-reperfusion injury, together with the accumulation of clinical evidence, led to the discovery of ischemic preconditioning, which has been the main hypothesis for over three decades for how ischemia-reperfusion injury can be attenuated. The subcellular pathophysiological mechanism of ischemia-reperfusion injury and preconditioning-induced cardioprotection is not well understood, but extensive research into components, including autacoids, ion channels, receptors, subcellular signaling cascades, and mitochondrial modulators, as well as strategies for modulating these components, has made evolutional progress. Owing to the accumulation of both basic and clinical evidence, the idea of ischemic postconditioning with a cardioprotective potential has been discovered and established, making it possible to apply this knowledge in the clinical setting after ischemia-reperfusion insult. Another a great outcome has been the launch of translational studies that apply basic findings for manipulating ischemia-reperfusion injury into practical clinical treatments against ischemic heart diseases. In this review, we discuss the current findings regarding the fundamental pathophysiological mechanisms of ischemia-reperfusion injury, the associated protective mechanisms of ischemic pre- and postconditioning, and the potential seeds for molecular, pharmacological, or mechanical treatments against ischemia-reperfusion injury, as well as subsequent adverse outcomes by modulation of subcellular signaling mechanisms (especially mitochondrial function). We also review emerging translational clinical trials and the subsistent clinical comorbidities that need to be overcome to make these trials applicable in clinical medicine.

Cardiac proteomic responses to ischemia-reperfusion injury and ischemic preconditioning

Cardiac ischemia and ischemia-reperfusion (I/R) injury are major contributors to morbidity and mortality worldwide. Pathological mechanisms of I/R and the physiological mechanisms of ischemic preconditioning (IPC), which is an effective cardiac protective response, have been widely investigated in the last decade to search for means to prevent or treat this disease. Proteomics is a powerful analytical tool that has provided important information to identify target proteins and understand the underlying mechanisms of I/R and IPC. Here, we review the application of proteomics to I/R injury and IPC to discover target proteins. We analyze the functional meaning of the accumulated data on hundreds of proteins using various bioinformatics applications. In addition, we review exercise-induced proteomic alterations in the heart to understand the potential cardioprotective role of exercise against I/R injury. Further developments in the proteomic field that target specialized proteins will yield new insights for optimizing therapeutic targets and developing a wide range of therapeutic agents against ischemic heart disease.

Exercise as a beneficial adjunct therapy during Doxorubicin treatment--role of mitochondria in cardioprotection

One of the mostly used chemotherapeutic drugs is the highly effective anthracycline Doxorubicin. However, its clinical use is limited by the dose-related and cumulative cardiotoxicity and consequent dysfunction. It has been proposed that the etiology of this toxicity is related to mitochondrial dysfunction. The present review aimed to analyze the promising results regarding the effect of several types of physical exercise in cardiac tolerance of animals treated with acute and sub-chronic doses of Doxorubicin (DOX), highlighting the importance of cardiac mitochondrial-related mechanisms in the process. Physical exercise positively modulates some important cardiac defense systems to antagonize the toxic effects caused by DOX treatment, including antioxidant capacity, the overexpression of heat shock proteins and other anti-apoptotic proteins. An important role in this protective phenotype afforded by exercise should be attributed to mitochondrial plasticity, as related adaptations could be translated into improved cardiac function in the setting of the DOX cardiomyopathy.

Drosophila as a model to study cardiac aging

With age, cardiac performance declines progressively and the risk of heart disease, a primary cause of mortality, rises dramatically. As the elderly population continues to increase, it is critical to gain a better understanding of the genetic influences and modulatory factors that impact cardiac aging. In an attempt to determine the relevance and utility of the Drosophila heart in unraveling the genetic mechanisms underlying cardiac aging, a variety of heart performance assays have recently been developed to quantify Drosophila heart performance that permit the use of the fruit fly to investigate the heart's decline with age. As for the human heart, Drosophila heart function also deteriorates with age. Notably, with progressive age the incidence of cardiac arrhythmias, myofibrillar disorganization and susceptibility to heart dysfunction and failure all increase significantly. We review here the evidence for an involvement of the insulin-TOR pathway, the K(ATP) channel subunit dSur, the KCNQ potassium channel, as well as Dystrophin and Myosin in fly cardiac aging, and discuss the utility of the Drosophila heart model for cardiac aging studies.

Moderate exercise prevents impaired Ca2+ handling in heart of CO-exposed rat: implication for sensitivity to ischemia-reperfusion

Sustained urban carbon monoxide (CO) exposure exacerbates heart vulnerability to ischemia-reperfusion via deleterious effects on the antioxidant status and Ca2+ homeostasis of cardiomyocytes. The aim of this work was to evaluate whether moderate exercise training prevents these effects. Wistar rats were randomly assigned to a control group and to CO groups, living during 4 wk in simulated urban CO pollution (30–100 parts/million, 12 h/day) with (CO-Ex) or sedentary without exercise (CO-Sed). The exercise procedure began 4 wk before CO exposure and was maintained twice a week in standard filtered air during CO exposure. On one set of rats, myocardial ischemia (30 min) and reperfusion (120 min) were performed on isolated perfused rat hearts. On another set of rats, myocardial antioxidant status and Ca2+ handling were evaluated following environmental exposure. As a result, exercise training prevented CO-induced myocardial phenotypical changes. Indeed, exercise induced myocardial antioxidant status recovery in CO-exposed rats, which is accompanied by a normalization of sarco(endo)plasmic reticulum Ca2+-ATPase 2a expression and then of Ca2+ handling. Importantly, in CO-exposed rats, the normalization of cardiomyocyte phenotype with moderate exercise was associated with a restored sensitivity of the myocardium to ischemia-reperfusion. Indeed, CO-Ex rats presented a lower infarct size and a significant decrease of reperfusion arrhythmias compared with their sedentary counterparts. To conclude, moderate exercise, by preventing CO-induced Ca2+ handling and myocardial antioxidant status alterations, reduces heart vulnerability to ischemia-reperfusion.

Acute exercise protects against calcium-induced cardiac mitochondrial permeability transition pore opening in doxorubicin-treated rats

The use of DOX (doxorubicin), an antibiotic used in oncological treatments, is limited by a dose-related cardiotoxicity against which acute exercise is protective. However, the mitochondrial-related mechanisms of this protection remain unknown. Therefore the present study aimed to determine the effects of an acute endurance exercise bout performed 24 h before DOX treatment on heart and liver mitochondrial function. A total of 20 adult male Wistar rats were divided into groups as follows: non-exercised with saline (NE + SAL), non-exercised DOX-treated (NE + DOX), exercised with saline (EX + SAL) and exercised DOX-treated (EX + DOX). The animals performed a 60 min exercise bout on a treadmill or remained sedentary 24 h before receiving either a DOX bolus (20 mg/kg of body weight) or saline. Heart and liver mitochondrial function [oxygen consumption, membrane potential (DeltaPsi) and cyclosporin-A-sensitive calcium-induced MPTP (mitochondrial permeability transition pore) opening] were evaluated. The activities of the respiratory complex, Mn-SOD (superoxide dismutase), caspases 3 and 9, as well as the levels of ANT (adenine nucleotide translocase), VDAC (voltage-dependent anion channel), CypD (cyclophilin D), Bax and Bcl-2, were measured. Acute exercise prevented the decreased cardiac mitochondrial function (state 3, phosphorylative lagphase; maximal DeltaPsi generated both with complex I- and II-linked substrates and calcium-induced MPTP opening) induced by DOX treatment. Exercise also prevented the DOX-induced decreased activity of cardiac mitochondrial chain complexes I and V, and increased caspase 3 and 9 activities. DOX administration and exercise caused increased cardiac mitochondrial SOD activity. Exercise ameliorated liver mitochondrial complex activities. No alterations were observed in the measured MPTP and apoptosis-related proteins in heart and liver mitochondria. The results demonstrate that acute exercise protects against cardiac mitochondrial dysfunction, preserving mitochondrial phosphorylation capacity and attenuating DOX-induced decreased tolerance to MPTP opening.

Influence of aerobic fitness on age-related lymphocyte DNA damage in humans: relationship with mitochondria respiratory chain and hydrogen peroxide production

The aim of this study was to analyze the influence of aerobic fitness (AF) on age-related lymphocyte DNA damage in humans, giving special attention to the role of the mitochondrial respiratory chain and hydrogen peroxide production. Considering age and AF (as assessed by VO(2)max), 66 males (19-59 years old) were classified as high fitness (HF) or low fitness (LF) and distributed into one of the following groups: young adults (19-29 years old), adults (30-39 years old), and middle-aged adults (over 40 years old). Peripheral lymphocytes obtained at rest were used to assess DNA damage (strand breaks and formamidopyrimidine DNA glycosylase (FPG) sites through the comet assay), activity of mitochondrial complexes I and II (polarographically measured), and the hydrogen peroxide production rate (assayed by fluorescence). Results revealed a significant interaction between age groups and AF for DNA strand breaks (F = 8.415, p = .000), FPG sites (F = 11.766, p = .000), mitochondrial complex I activity (F = 7.555, p = .000), and H(2)O(2) production (F = 7.500, p = .000). Except for mitochondrial complex II activity, the age variation of the remaining parameters was significantly attenuated by HF. Considering each AF level, an increase in DNA strand breaks and FPG sites with age (r = 0.655, p = 0.000, and r = 0.738, p = 0.000, respectively) was only observed in LF. Moreover, decreased mitochondrial complex I activity with age (r = -.470, p = .009) was reported in LF. These results allow the conclusion that high AF seems to play a key role in attenuating the biological aging process.

Drosophila as a model for age-related impairment in locomotor and other behaviors

Aging is a multifaceted phenomenon that occurs in most species including humans and the fruit fly, Drosophila melanogaster. One of the most fundamental features of aging is the progressive decline in functional capacity that occurs with age (i.e. functional senescence). Age-related declines in function undermine many aspects of normal youthful physiology including behavior. Age-related behavioral declines are quite telling because they presumably reflect primary functional defects in the nervous system or musculature. Consequently, a more detailed understanding of behavioral declines that occur with age, including mechanisms that impinge on them, could ultimately lead to improved treatment or diagnosis of age-related defects in physiological processes that depend on normal function of the nervous system or musculature. Such advances in diagnosis or treatment would translate into tremendous gains in quality of life for elderly populations. In this article, we review progress using Drosophila to better understand age-related behavioral declines with a focus on age-related locomotor impairment.

Triggering endogenous neuroprotective processes through exercise in models of dopamine deficiency

We are testing the hypothesis that exercise is neuroprotective in animal models of the dopamine (DA) deficiency in Parkinson's disease. Our studies include mice or rats provided access to a running wheel and subsequently treated with MPTP (mice) or 6-hydroxydopamine (rats) and monkeys provided access to a treadmill and subsequently treated with MPTP. Typically, the exercise occurs for 3 months prior to the toxin treatment and often for 1-2 months thereafter. Our findings indicate that exercise reduces the behavioral impairments elicited by the dopaminergic neurotoxins as well as the loss of DA neurons as assessed by PET imaging and biochemical or histochemical assessment of tissue samples. Our studies are focused on one of several possible explanations for the beneficial effects of exercise: an exercise-induced increase in the expression of neurotrophic factors, particularly GDNF. Our observations indicate that GDNF can reduce the vulnerability of DA neurons, in part due to the activation of key intracellular cascades. We also find that mild cellular stress itself can provide protection against more intensive stress, a form of preconditioning. We conclude that dopamine neurons have the capacity to respond to intracellular and extracellular signals by triggering endogenous neuroprotective mechanisms. This raises the possibility that some individuals with Parkinson's disease suffer from a reduction of these neuroprotective mechanisms, and that treatments that boost these mechanisms - including exercise - may provide therapeutic benefit.

Melatonin reduces cardiac inflammatory injury induced by acute exercise

Cardiac muscle tissue, when stimulated by acute exercise, presents increased signs of cell damage. This study was designed to investigate whether overexpression of inflammatory mediators induced in the heart by acute exercise could be prevented by melatonin and whether the protective effect of melatonin was related with inhibition of nuclear factor kappa B (NF-kappaB) activation. Male Wistar rats received melatonin i.p. at a dose of 1.0 mg/kg body weight 3 min before being exercised for 60 min on a treadmill at a speed of 25 m/min and a 10% slope. Exercise was associated with a significant increase in myeloperoxidase activity and in TNF-alpha, IL-1 and IL-6 mRNA levels. Both mRNA level and protein concentrations of intercellular adhesion molecule-1, inducible nitric oxide synthase, and cyclooxygenase-2 were also significantly elevated. A significant activation of nuclear factor kappa B (NF-kappaB) was observed in exercised rats. These effects were totally or partially prevented by melatonin administration. Data obtained indicate that melatonin protects against heart damage caused by acute exercise. Impaired production of noxious mediators involved in the inflammatory process and down-regulation of the NF-kappaB signal transduction pathway appear to contribute to the beneficial effects of melatonin.

Exercise-training in young Drosophila melanogaster reduces age-related decline in mobility and cardiac performance

Declining mobility is a major concern, as well as a major source of health care costs, among the elderly population. Lack of mobility is a primary cause of entry into managed care facilities, and a contributing factor to the frequency of damaging falls. Exercise-based therapies have shown great promise in sustaining mobility in elderly patients, as well as in rodent models. However, the genetic basis of the changing physiological responses to exercise during aging is not well understood. Here, we describe the first exercise-training paradigm in an invertebrate genetic model system. Flies are exercised by a mechanized platform, known as the Power Tower, that rapidly, repeatedly, induces their innate instinct for negative geotaxis. When young flies are subjected to a carefully controlled, ramped paradigm of exercise-training, they display significant reduction in age-related decline in mobility and cardiac performance. Fly lines with improved mitochondrial efficiency display some of the phenotypes observed in wild-type exercised flies. The exercise response in flies is influenced by the amount of protein and lipid, but not carbohydrate, in the diet. The development of an exercise-training model in Drosophila melanogaster opens the way to direct testing of single-gene based genetic therapies for improved mobility in aged animals, as well as unbiased genetic screens for loci involved in the changing response to exercise during aging.

Cardioprotection requires taking out the trash

Autophagy is a critical cellular housekeeping process that is essential for removal of damaged or unwanted organelles and protein aggregates. Under conditions of starvation, it is also a mechanism to break down proteins to generate amino acids for synthesis of new and more urgently needed proteins. In the heart, autophagy is upregulated by starvation, reactive oxygen species, hypoxia, exercise, and ischemic preconditioning, the latter a well-known potent cardioprotective phenomenon. The observation that upregulation of autophagy confers protection against ischemia/reperfusion injury and inhibition of autophagy is associated with a loss of cardioprotection conferred by pharmacological conditioning suggests that the pathway plays a key role in enhancing the heart's tolerance to ischemia. While many of the antecedent signaling pathways of preconditioning are well-defined, the mechanisms by which preconditioning and autophagy converge to protect the heart are unknown. In this review we discuss mechanisms that potentially underlie the linkage between cardioprotection and autophagy in the heart.

Autophagy in ischemic heart disease

Autophagy is a major catabolic pathway by which mammalian cells degrade and recycle macromolecules and organelles. It plays a critical role in removing protein aggregates, as well as damaged or excess organelles, to maintain intracellular homeostasis and to keep the cell healthy. In the heart, autophagy occurs at low levels under normal conditions, and defects in this process cause cardiac dysfunction and heart failure. However, this pathway is rapidly upregulated under environmental stress conditions, including ATP depletion, reactive oxygen species, and mitochondrial permeability transition pore opening. Although autophagy is enhanced in various pathophysiological conditions, such as during ischemia and reperfusion, the functional role of increased autophagy is not clear and is currently under intense investigation. In this review, we discuss the evidence for autophagy in the heart in response to ischemia and reperfusion, identify factors that regulate autophagy, and analyze the potential roles autophagy might play in cardiac cells.

Beneficial effects of exercise on muscle mitochondrial function in diabetes mellitus

The physiopathology of diabetes mellitus has been closely associated with a variety of alterations in mitochondrial histology, biochemistry and function. Generally, the alterations comprise increased mitochondrial reactive oxygen and nitrogen species (RONS) generation, resulting in oxidative stress and damage; decreased capacity to metabolize lipids, leading to intramyocyte lipid accumulation; and diminished mitochondrial density and reduced levels of uncoupling proteins (UCPs), with consequent impairment in mitochondrial function. Chronic physical exercise is a physiological stimulus able to induce mitochondrial adaptations that can counteract the adverse effects of diabetes on muscle mitochondria. However, the mechanisms responsible for mitochondrial adaptations in the muscles of diabetic patients are still unclear. The main mechanisms by which exercise may be considered an important non-pharmacological strategy for preventing and/or attenuating diabetes-induced mitochondrial impairments may involve (i) increased mitochondrial biogenesis, which is dependent on the increased expression of some important proteins, such as the 'master switch' peroxisome proliferator-activated receptor (PPAR)-gamma-coactivator-1alpha (PGC-1alpha) and heat shock proteins (HSPs), both of which are severely downregulated in the muscles of diabetic patients; and (ii) the restoration or attenuation of the low UCP3 expression in skeletal muscle mitochondria of diabetic patients, which is suggested to play a pivotal role in mitochondrial dysfunction.There is evidence that chronic exercise and lifestyle interventions reverse impairments in mitochondrial density and size, in the activity of respiratory chain complexes and in cardiolipin content; however, the mechanisms by which chronic exercise alters mitochondrial respiratory parameters, mitochondrial antioxidant systems and other specific proteins involved in mitochondrial metabolism in the muscles of diabetic patients remain to be elucidated.

Effects of physical exercise on myocardial telomere-regulating proteins, survival pathways, and apoptosis

OBJECTIVES

The purpose of this study was to study the underlying molecular mechanisms of the protective cardiac effects of physical exercise.

BACKGROUND

Telomere-regulating proteins affect cellular senescence, survival, and regeneration.

METHODS

C57/Bl6 wild-type, endothelial nitric oxide synthase (eNOS)-deficient and telomerase reverse transcriptase (TERT)-deficient mice were randomized to voluntary running or no running wheel conditions (n = 8 to 12 per group).

RESULTS

Short-term running (21 days) up-regulated cardiac telomerase activity to >2-fold of sedentary controls, increased protein expression of TERT and telomere repeat binding factor (TRF) 2, and reduced expression of the proapoptotic mediators cell-cycle-checkpoint kinase 2 (Chk2), p53, and p16. Myocardial and leukocyte telomere length did not differ between 3-week- and 6-month-old sedentary or running mice, but telomerase activity, TRF2 and TERT expression were persistently increased after 6 months and the expression of Chk2, p53, and p16 remained down-regulated. The exercise-induced changes were absent in both TERT(-/-) and eNOS(-/-) mice. Running increased cardiac expression of insulin-like growth factor (IGF)-1. Treatment with IGF-1 up-regulated myocardial telomerase activity >14-fold and increased the expression of phosphorylated Akt protein kinase and phosphorylated eNOS. To test the physiologic relevance of these exercise-mediated prosurvival pathways, apoptotic cardiomyopathy was induced by treatment with doxorubicin. Up-regulation of telomere-stabilizing proteins by physical exercise in mice reduced doxorubicin-induced p53 expression and potently prevented cardiomyocyte apoptosis in wild-type, but not in TERT(-/-) mice.

CONCLUSIONS

Long- and short-term voluntary physical exercise up-regulates cardiac telomere-stabilizing proteins and thereby induces antisenescent and protective effects, for example, to prevent doxorubicin-induced cardiomyopathy. These beneficial cardiac effects are mediated by TERT, eNOS, and IGF-1.

Exercise restores coronary vascular function independent of myogenic tone or hyperglycemic status in db/db mice

Regulation of coronary function in diabetic hearts is an important component in preventing ischemic cardiac events but remains poorly studied. Exercise is recommended in the management of diabetes, but its effects on diabetic coronary function are relatively unknown. We investigated coronary artery myogenic tone and endothelial function, essential elements in maintaining vascular fluid dynamics in the myocardium. We hypothesized that exercise reduces pressure-induced myogenic constriction of coronary arteries while improving endothelial function in db/db mice, a model of type 2 diabetes. We used pressurized mouse coronary arteries isolated from hearts of control and db/db mice that were sedentary or exercised for 1 h/day on a motorized exercise-wheel system (set at 5.2 m/day, 5 days/wk). Exercise caused a approximately 10% weight loss in db/db mice and decreased whole body oxidative stress, as measured by plasma 8-isoprostane levels, but failed to improve hyperglycemia or plasma insulin levels. Exercise did not alter myogenic regulation of arterial diameter stimulated by increased transmural pressure, nor did it alter smooth muscle responses to U-46619 (a thromboxane agonist) or sodium nitroprusside (an endothelium-independent dilator). Moderate levels of exercise restored ACh-simulated, endothelium-dependent coronary artery vasodilation in db/db mice and increased expression of Mn SOD and decreased nitrotyrosine levels in hearts of db/db mice. We conclude that the vascular benefits of moderate levels of exercise were independent of changes in myogenic tone or hyperglycemic status and primarily involved increased nitric oxide bioavailability in the coronary microcirculation.