Exercise training-induced enhancement in myocardial mechanics is lost after 2 weeks of detraining in rats

Effects of physical training on the metabolic profile of rats exposed to chronic restraint stress

INTRODUCTION

Despite strong evidences supporting the protective role of exercise against stress-induced repercussions, the literature remains inconclusive regarding metabolic aspects. Therefore, this study aimed to evaluate the effect of Physical Training (PT) by swimming on the metabolic parameters of rats subjected to restraint stress.

METHODS

Wistar rats (n = 40) were divided into four groups: Control (C), Trained (T), Stressed (S), and Trained/Stressed (TS). The restraint stress protocol involved confining the animals in PVC pipes for 60 minutes/day for 12 weeks. Concurrently, the swimming PT protocol was performed without additional load in entailed sessions of 60 minutes conducted five days a week for the same duration. The following parameters were analyzed: fitness progression assessed by the physical capacity test, body mass, serum level of glucose, triglyceride, cholesterol and corticosterone, as well as glycemic tolerance test, evaluated after glucose administration (2 g/kg, i.p.).

RESULTS

Trained groups (T and TS) exhibited enhanced physical capacity (169 ± 21 and 162 ± 22% increase, respectively) compared to untrained groups (C: 9 ± 5 and S: 11 ± 13% increase). Corticosterone levels were significantly higher in the S group (335 ± 9 nmoL/L) compared to C (141 ± 3 nmoL/L), T (174 ± 3 nmoL/L) and TS (231 ± 7 nmoL/L), which did not differ from each other. There were no significant changes in serum glucose, cholesterol, and triglyceride levels among the groups. However, the glycemic curve after glucose loading revealed increased glycemia in the S group (area under curve 913 ± 30 AU) but the TS group exhibited values (673 ± 12 AU) similar to the groups C (644 ± 10 AU) and T (649 ± 9 AU).

CONCLUSION

Swimming-based training attenuated stress-induced corticosterone release and prevented glucose intolerance in rats, reinforcing the importance of exercise as a potential strategy to mitigate the pathophysiological effects of stress.

Strength training improves heart function, collagen and strength in rats with heart failure

BACKGROUND/OBJECTIVES

Myocardial infarction (MI) frequently leads to cardiac remodeling and failure with impaired life quality, playing an important role in cardiovascular deaths. Although physical exercise is a well-recognized effective non-pharmacological therapy for cardiovascular diseases, the effects of strength training (ST) on the structural and functional aspects of cardiac remodeling need to be further documented. In this study, we aimed to investigate the role of a linear block ST protocol in the rat model of MI.

METHODS AND RESULTS

After 6 weeks of MI induction or sham surgery, male adult rats performed ST for the following 12 weeks. The ladder-based ST program was organized in three mesocycles of 4 weeks, with one load increment for each block according to the maximal carrying load test. After 12 weeks, the infarcted-trained rats exhibited an increase in performance, associated with reduced cardiac hypertrophy and pulmonary congestion compared with the untrained group. Despite not changing MI size, the ST program partially prevented cardiac dilatation and ventricular dysfunction assessed by echocardiography and hemodynamics, and interstitial fibrosis evaluated by histology. In addition, isolated cardiac muscles from infarcted-trained rats had improved contractility parameters in a steady state, and in response to calcium or stimuli pauses.

CONCLUSIONS

The ST in infarcted rats increased the capacity to carry mass, associated with attenuation of cardiac remodeling and pulmonary congestion with improving cardiac function that could be attributed, at least in part, to the improvement of myocardial contractility.

Long-term detraining reverses the improvement of lifelong exercise on skeletal muscle ferroptosis and inflammation in aging rats: fiber-type dependence of the Keap1/Nrf2 pathway

We investigated the effects of lifelong aerobic exercise and 8 months of detraining after 10 months of aerobic training on circulation, skeletal muscle oxidative stress, and inflammation in aging rats. Sprague-Dawley rats were randomly assigned to the control (CON), detraining (DET), and lifelong aerobic training (LAT) groups. The DET and LAT groups began aerobic treadmill exercise at the age of 8 months and stopped training at the 18th and 26th month, respectively; all rats were sacrificed when aged 26 months. Compared with CON, LAT remarkably decreased serum and aged skeletal muscle 4-hydroxynonenal (4-HNE) and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. Superoxide dismutase 2(SOD2) levels were higher in the LAT group than in the CON group in skeletal muscle. However, DET remarkably decreased SOD2 protein expression and content in the skeletal muscle and increased malondialdehyde (MDA) level compared with LAT. Compared with LAT, DET remarkably downregulated adiponectin and upregulated tumor necrosis factor alpha (TNF-α) expression, while phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and 70-kDa ribosomal protein S6 kinase (P70S6K) protein expression decreased, and that of FoxO1 and muscle atrophy F-box (MAFbX) proteins increased in the quadriceps femoris. Adiponectin and TNF-α expression in the soleus muscle did not change between groups, whereas that of AKT, mammalian target of rapamycin (mTOR), and P70S6K was lower in the soleus in the DET group than in that in the LAT group. Compared with that in the LAT group, sestrin1 (SES1) and nuclear factor erythroid 2-related factor 2 (Nrf2) protein expression in the DET group was lower, whereas Keap1 mRNA expression was remarkably upregulated in the quadriceps femoris. Interestingly, the protein and mRNA levels of SES1, Nrf2, and Keap1 in soleus muscle did not differ between groups. LAT remarkably upregulated ferritin heavy polypeptide 1(FTH), glutathione peroxidase 4(GPX4), and solute carrier family 7member 11 (SLC7A11) protein expression in the quadriceps femoris and soleus muscles, compared with CON. However, compared with LAT, DET downregulated FTH, GPX4, and SLC7A11 protein expression in the quadriceps femoris and soleus muscles. Long-term detraining during the aging phase reverses the improvement effect of lifelong exercise on oxidative stress, inflammation, ferroptosis, and muscle atrophy in aging skeletal muscle. The quadriceps femoris is more evident than the soleus, which may be related to the different changes in the Keap1/Nrf2 pathway in different skeletal muscles.

Effects of detraining on preconditioning exercise-induced neuroprotective potential after ischemic stroke in rats

Preconditioning exercise prior to stroke exerts neuroprotection, which is an endogenous strategy that leads the brain cells to express several intrinsic factors and inhibits their apoptosis. However, it is unclear how long these benefits last after exercise cessation. The aim of this study was to investigate the effects of detraining on preconditioning exercise-induced neuroprotective potential after stroke. Rats were trained using a treadmill for aerobic exercise 5 days each week for 3 weeks, and their neuroprotective effects were examined until 3 weeks after exercise cessation. Stroke was induced by 60 min of left middle cerebral artery occlusion at 3 days, 1, 2, and 3 weeks after exercise cessation. Infarct volume, neurological deficits, sensorimotor function, expression levels of brain-derived neurotrophic factor (BDNF), hypoxia-induced factor-1α (HIF-1α), glial fibrillary acidic protein (GFAP), and P2X7 receptors, and apoptosis activity were examined using immunohistochemical and western blot analyses. Preconditioning exercise significantly reduced infarct volume and ameliorated sensorimotor function after stroke, and its beneficial effects were observed until 2 weeks after exercise cessation. The expression level of BDNF in the ischemic brain was significantly upregulated at 3 days after exercise cessation; however, the expression levels of HIF-1α, GFAP, and P2X7 receptor were significantly increased until 2 weeks after exercise cessation; thereby, significant anti-apoptotic effects were lost at 3 weeks of detraining. Our findings suggest that preconditioning exercise-induced neuroprotective potential may be lost shortly after exercise cessation. Neuroprotection through intrinsic protective factors, such as BDNF and HIF-1α, may provide different neuroprotective mechanisms in a time-dependent manner during detraining.

Aerobic exercise training reduces cardiac function and coronary flow-induced vasodilation in mice lacking adiponectin

We tested the hypothesis that adiponectin deficiency attenuates cardiac and coronary microvascular function and prevents exercise training-induced adaptations of the myocardium and the coronary microvasculature in adult mice. Adult wild-type (WT) or adiponectin knockout (adiponectin KO) mice underwent treadmill exercise training or remained sedentary for 8-10 wk. Systolic and diastolic functions were assessed before and after exercise training or cage confinement. Vasoreactivity of coronary resistance arteries was assessed at the end of exercise training or cage confinement. Before exercise training, ejection fraction and fractional shortening were similar in adiponectin KO and WT mice, but isovolumic contraction time was significantly lengthened in adiponectin KO mice. Exercise training increased ejection fraction (12%) and fractional shortening (20%) with no change in isovolumic contraction time in WT mice. In adiponectin KO mice, both ejection fraction (-9%) and fractional shortening (-12%) were reduced after exercise training and these decreases were coupled to a further increase in isovolumic contraction time (20%). In sedentary mice, endothelium-dependent dilation to flow was higher in arterioles from adiponectin KO mice as compared with WT mice. Exercise training enhanced dilation to flow in WT mice but decreased flow-induced dilation in adiponectin KO mice. These data suggest that compensatory mechanisms contribute to the maintenance of cardiac and coronary microvascular function in sedentary mice lacking adiponectin; however, in the absence of adiponectin, cardiac and coronary microvascular adaptations to exercise training are compromised.NEW & NOTEWORTHY We report that compensatory mechanisms contribute to the maintenance of cardiac and coronary microvascular function in sedentary mice in which adiponectin has been deleted; however, when mice lacking adiponectin are subjected to the physiological stress of exercise training, beneficial coronary microvascular and cardiac adaptations are compromised or absent.

Linear periodization of strength training in blocks attenuates hypertension and diastolic dysfunction with normalization of myocardial collagen content in spontaneously hypertensive rats

BACKGROUND AND METHOD

This study evaluated the effects of a linear block strength training programme on the parameters of cardiac remodelling in spontaneously hypertensive rats. Thirty-nine rats were equally distributed in four groups: normotensive sedentary, normotensive trained, hypertensive sedentary and hypertensive trained. The strength training protocol was organized in three mesocycles of 4 weeks, with an increase in the training load organized in a linear fashion for each block, considering the weight established in the maximum loaded load test. The following parameters were evaluated: ventricular function assessed by echocardiogram, caudal blood pressure, ventricular haemodynamics and cardiac masses. Two-way analysis of variance was used to determine the differences between the group and time.

RESULTS

After 12 weeks of training, the hypertensive trained group presented the following results: increased muscle strength, reduced blood pressure, reduced heart rate, isovolumetric relaxation time and total collagen content, with increased cardiac function, without promoting changes in the mass and nuclear volume of cardiomyocytes. Also, blood pressure reduction seems to be associated with both muscle strength adjustments and total load progress.

CONCLUSION

The findings of this study showed that the training programme carried out attenuated systemic arterial pressure and preserved the ventricular function of spontaneously hypertensive rats without cardiac mass change.

Short-Term Cigarette Smoking in Rats Impairs Physical Capacity and Induces Cardiac Remodeling

Despite the strong evidence on the cardiac and renal damages after chronic exposure to cigarette smoke, there is a paucity of data on its short-term effects. The study evaluated the short-term effects of cigarette smoking on left ventricular (LV) remodeling, in vitro myocardial and renal function. Female Wistar rats were randomized to control (C) and cigarette smoking rats for eight weeks. Physical capacity was assessed using an adapted model of exhaustive swim; left ventricle (LV) morphology and function were also evaluated. Renal function was assessed by creatinine clearance and urine protein. The in vitro myocardial performance was analyzed in isolated papillary muscles. Rats exhibited reduced physical capacity after short-term cigarette smoking. Although there was no change on LV function, reduced chamber diameter was found in the smoking group associated with an increased LV wall thickness. There was augmented cardiac mass compared to C that was confirmed by increased cardiomyocyte nucleus volume, but in vitro myocardial performance and renal function were unchanged. A short-term cigarette smoking induces cardiac remodeling without abnormalities in function. The smoking group still preserved renal function and in vitro myocardial performance. However, the reduced physical capacity may suggest an impairment of the cardiac reserve.

Aerobic exercise improves memory and prevents cognitive deficits of relevance to schizophrenia in an animal model

INTRODUCTION AND OBJECTIVES

Cognitive impairment associated with schizophrenia (CIAS) greatly reduces patients' functionality, and remains an unmet clinical need. The sub-chronic phencyclidine (scPCP) rat model is commonly employed in studying CIAS. We have previously shown that voluntary exercise reverses impairments in novel object recognition (NOR) induced by scPCP. However, there has not been a longitudinal study investigating the potential protective effects of exercise in a model of CIAS. This study aimed to investigate the pro-cognitive and protective effects of exercise on CIAS using the translational NOR and attentional set-shifting tasks (ASST).

METHODS

Female Lister Hooded rats were either exercised (wheel running for one hour per day, five days per week, for six weeks; n=20) or not (n=20) and then tested in a natural-forgetting NOR test. Rats in each group were then administered either PCP (2 mg/kg intraperitoneally (i.p.)) or saline solution (1 mL/kg i.p.) for seven days, followed by seven days washout. Three NOR tests were conducted immediately and two and nine weeks after washout, and a natural-forgetting NOR test was carried out again eight weeks post washout. Rats were trained and tested in ASST from week 6 to week 10 post washout.

RESULTS

Non-exercised rats displayed a deficit in both of the natural-forgetting NOR tests, whereas exercised rats did not. The scPCP exercise group did not show the expected deficit in NOR at any time point, and had a significantly ameliorated deficit in the ASST compared to the scPCP control group.

CONCLUSION

Voluntary exercise has long-lasting pro-cognitive and protective effects in two cognitive domains. Exercise improves cognition and could provide protection against CIAS.

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.

Delayed Reperfusion-Coronary Artery Reperfusion Close to Complete Myocardial Necrosis Benefits Remote Myocardium and Is Enhanced by Exercise

The present study aimed to analyze the effects of reperfusion of a distant coronary artery on cardiac function, the ultrastructure, and the molecular environment of the remote myocardium immediately after the completion of myocardial regional necrosis: delayed reperfusion (DR). Additionally, the effects of prior exercise on the outcomes of DR were investigated. Female rats with permanent occlusion or delayed reperfusion were randomly assigned to an exercise (swimming, 1 h/day, 5 days/week for 8 weeks) or sedentary protocol. Thus, the study included the following four groups: sedentary permanent occlusion, exercise permanent occlusion, sedentary delayed reperfusion, and exercise delayed reperfusion. The descending coronary artery was occluded for 1 h. Reperfusion was confirmed by contrast echocardiography, and the rats were observed for 4 weeks. Permanent occlusion and DR caused similar myocardial infarction sizes among the four groups. Interestingly, exercise significantly decreased the mortality rate. Delayed reperfusion resulted in significant benefits, including enhanced hemodynamics and papillary muscle contraction, as well as reduced apoptosis and collagen content. Protein calcium kinetics did not change. Meanwhile, developed tension and the Frank–Starling mechanism were enhanced, suggesting that calcium sensitivity was intensified in myofilaments. Remarkable remote myocardial benefits occurred after distant DR, and prior exercise intensified cardiac recovery. Our findings provide valuable information about DR. Our data might explain the better clinical outcomes in recent studies showing that late reperfusion could improve heart failure in patients with myocardial infarction. In conclusion, DR has remote myocardial benefits, including inotropism enhancement, pulmonary congestion reduction, and collagen and apoptosis attenuation, which are enhanced by prior exercise.

Moderate Physical Training Ameliorates Cardiovascular Dysfunction Induced by High Fat Diet After Cessation of Training in Adult Rats

We aimed to test whether moderate physical training can induce long-lasting protection against cardiovascular risk factors induced by high fat diet (HFD) intake, even after cessation of training. 90-days-old Wistar rats were submitted to a sedentary lifestyle or moderate physical training, three times a week, for 30 days. Following this, at 120 days-of age, sedentary and trained rats received a hypercaloric diet (HFD) or a commercial diet normal fat diet (NFD) for 30 days. Body weight (BW) and food intake were evaluated weekly. At 150 days-of age, hemodynamic measures (systolic, diastolic, mean blood pressure, pulse pressure, pulse interval and heart rate) were made via an indwelling femoral artery catheter. Beat-to-beat data were analyzed to calculate power spectra of systolic blood pressure (SBP) and pulse interval. After euthanasia, mesenteric fat pads were removed and weighted and total blood was stored for later analysis of lipid profile. Consumption of a HFD increased blood pressure (BP), pulse pressure, low frequency BP variability, BW gain, fat pad stores and induced dyslipidemia. Interestingly, prior physical training was able to partially protect against this rise in BP and body fat stores. Prior physical training did not totally protect against the effects of HFD consumption but previously trained animals did demonstrate resistance to the development of cardiometabolic alterations, which illustrate that the benefits of physical training may be partially maintained even after 30 days of detraining period.

Endurance training restores spatially distinct cardiac mitochondrial function and myocardial contractility in ovariectomized rats

We previously demonstrated that the loss of female hormones induces cardiac and mitochondrial dysfunction in the female heart. Here, we show the impact of endurance training for twelve weeks, a nonpharmacological therapy against cardiovascular disease caused by ovariectomy and its contribution to cardiac contractility, mitochondrial quality control, bioenergetics and oxidative damage. We found that ovariectomy induced cardiac hypertrophy and dysfunction by decreasing SERCA2 and increasing phospholamban protein expression. Endurance training restored myocardial contractility, SERCA2 levels, increased calcium transient in ovariectomized rats but did not change phospholamban protein expression or cardiac hypertrophy. Additionally, ovariectomy decreased the amount of intermyofibrillar mitochondria and induced mitochondrial fragmentation that were accompanied by decreased levels of mitofusin 1, PGC-1α, NRF-1, total AMPK-α and mitochondrial Tfam. Endurance training prevented all these features except for mitofusin 1. Ovariectomy reduced O₂ consumption, elevated O₂^.- release and increased Ca²⁺-induced mitochondrial permeability transition pore opening in both mitochondrial subpopulations. Ovariectomy also increased NOX-4 protein expression in the heart, reduced mitochondrial Mn-SOD, catalase protein expression and increased protein carbonylation in both mitochondrial subpopulations, which were prevented by endurance training. Taken together, our findings show that endurance training prevented cardiac contractile dysfunction and mitochondrial quality control in ovariectomized rats.

Characterization of the dynamic changes in left ventricular morphology and function induced by exercise training and detraining

BACKGROUND

Although exercise-induced cardiac hypertrophy has been intensively investigated, its development and regression dynamics have not been comprehensively described. In the current study, we aimed to characterize the effects of regular exercise training and detraining on left ventricular (LV) morphology and function.

METHODS

Rats were divided into exercised (n = 12) and control (n = 12) groups. Exercised rats swam 200 min/day for 12 weeks. After completion of the training protocol, rats remained sedentary for 8 weeks (detraining period). Echocardiographic follow-up was performed regularly to obtain LV long- and short-axis recordings for speckle-tracking echocardiography analysis. Global longitudinal and circumferential strain and systolic strain rate were measured. LV pressure-volume analysis was performed using additional groups of rats to obtain haemodynamic data.

RESULTS

Echocardiographic examinations showed the development of LV hypertrophy in the exercised group. These differences disappeared during the detraining period. Strain and strain rate values were all increased after the training period, whereas supernormal values rapidly reversed to the control level after training cessation. Load-independent haemodynamic indices, e.g., preload recruitable stroke work, confirmed the exercise-induced systolic improvement and complete regression after detraining.

CONCLUSIONS AND TRANSLATIONAL ASPECT

Our results provide the first comprehensive data to describe the development and regression dynamics of morphological and functional aspects of physiological hypertrophy in detail. Speckle-tracking echocardiography has been proven to be feasible to follow-up changes induced by exercise training and detraining and might provide an early possibility to differentiate between physiological and pathological conditions.

Contribution of Heme Oxygenase 2 to Blood Pressure Regulation in Response to Swimming Exercise and Detraining in Spontaneously Hypertensive Rats

Background

We aimed to determine the effects of exercise followed by detraining on systolic blood pressure (SBP), heme oxygenase 2 (HO-2) expression, and carboxyhemoglobin (COHb) concentration in spontaneously hypertensive rats (SHR) to explain the role of carbon monoxide (CO) in this process.

Material/Methods

Animals were randomized into exercised and detrained groups. Corresponding sedentary rats were grouped as Time 1–2. Swimming of 60 min/5 days/week for 10 weeks was applied. Detraining rats discontinued training for an additional 5 weeks. Gene and protein expressions were determined by real-time PCR and immunohistochemistry.

Results

Aorta HO-2 histological scores (HSCORE) of hypertensive rats were lower, while SBP was higher. Swimming caused enhancement of HO-2 immunostaining in aorta endothelium and adventitia of SHR. Exercise induced elevation of blood COHb index in SHR. Synchronous BP lowering effect of exercise was observed. HO-2 mRNA expression, HSCORE, and blood COHb index were unaltered during detraining, while SBP was still low in SHR.

Conclusions

CO synthesized by HO-2 at least partly plays a role in SBP regulation in the SHR- and BP-lowering effect of exercise. Regular exercise with short-term pauses may be advised to both hypertensives and individuals who are at risk.

Swimming Training Improves Myocardial Mechanics, Prevents Fibrosis, and Alters Expression of Ca2+ Handling Proteins in Older Rats

Exercise training effects on the contractility of aged myocardium have been investigated for more than 20 years, but the data are still unclear. This study evaluated the hypothesis that a swimming training (ST) may improve myocardial inotropism in older rats. Male Wistar rats aged 4 (young)-and 21 (old)-months-old were divided into young untrained (YNT), old untrained (ONT), and old trained (OTR; 6 weeks of ST) groups. Echocardiography and hemodynamic were employed to assess left ventricular morphology and function. Myocardial mechanics was evaluated on papillary muscles. Histological and immunoblotting were carried out to evaluate fibrosis and proteins that modulate the myocardial function and calcium handling. We found that older rats did not show cardiac dysfunction, but ONT group showed lower physical performance during a swimming test (YNT: 5 ± 2; ONT: -16 ± 0.4; OTR: 51 ± 3; Δ%, sec). Moreover, ONT group showed worse myocardial inotropism, in which it was reversed by ST (Peak developed tension: YNT: 6.2 ± 0.7; ONT: 3.9 ± 0.3; OTR: 6.9 ± 0.9; g/mm2). The ST was associated with preserved collagen content (YNT: 0.38 ± 0.05; ONT: 0.78 ± 0.12; OTR: 0.34 ± 0.09; %). Exercise partially mitigated the effects of aging on intracellular Ca2+-regulating protein (eg, L-Ca2+ channel and phospholamban) and β-isoform of myosin. Thus, we propose that these molecular alterations together with inhibition of collagen increase contribute to improved myocardial performance in older rats.

Sustained cardiac programming by short-term juvenile exercise training in male rats

KEY POINTS

Cardiac hypertrophy following endurance-training is thought to be due to hypertrophy of existing cardiomyocytes. The benefits of endurance exercise on cardiac hypertrophy are generally thought to be short-lived and regress to sedentary levels within a few weeks of stopping endurance training. We have now established that cardiomyocyte hyperplasia also plays a considerable role in cardiac growth in response to just 4 weeks of endurance exercise in juvenile (5-9 weeks of age) rats. The effect of endurance exercise on cardiomyocyte hyperplasia diminishes with age and is lost by adulthood. We have also established that the effect of juvenile exercise on heart mass is sustained into adulthood.

ABSTRACT

The aim of this study was to investigate if endurance training during juvenile life 'reprogrammes' the heart and leads to sustained improvements in the structure, function, and morphology of the adult heart. Male Wistar Kyoto rats were exercise trained 5 days week^-1 for 4 weeks in either juvenile (5-9 weeks of age), adolescent (11-15 weeks of age) or adult life (20-24 weeks of age). Juvenile exercise training, when compared to 24-week-old sedentary rats, led to sustained increases in left ventricle (LV) mass (+18%; P < 0.05), wall thickness (+11%; P < 0.05), the longitudinal area of binucleated cardiomyocytes (P < 0.05), cardiomyocyte number (+36%; P < 0.05), and doubled the proportion of mononucleated cardiomyocytes (P < 0.05), with a less pronounced effect of exercise during adolescent life. Adult exercise training also increased LV mass (+11%; P < 0.05), wall thickness (+6%; P < 0.05) and the longitudinal area of binucleated cardiomyocytes (P < 0.05), despite no change in cardiomyocyte number or the proportion of mono- and binucleated cardiomyocytes. Resting cardiac function, LV chamber dimensions and fibrosis levels were not altered by juvenile or adult exercise training. At 9 weeks of age, juvenile exercise significantly reduced the expression of microRNA-208b, which is a known regulator of cardiac growth, but this was not sustained to 24 weeks of age. In conclusion, juvenile exercise leads to physiological cardiac hypertrophy that is sustained into adulthood long after exercise training has ceased. Furthermore, this cardiac reprogramming is largely due to a 36% increase in cardiomyocyte number, which results in an additional 20 million cardiomyocytes in adulthood.

Complete Reversion of Cardiac Functional Adaptation Induced by Exercise Training

PURPOSE

Long-term exercise training is associated with characteristic cardiac adaptation, termed athlete's heart. Our research group previously characterized in vivo left ventricular (LV) function of exercise-induced cardiac hypertrophy in detail in a rat model; however, the effect of detraining on LV function is still unclear. We aimed at evaluating the reversibility of functional alterations of athlete's heart after detraining.

METHODS

Rats (n = 16) were divided into detrained exercised (DEx) and detrained control (DCo) groups. Trained rats swam 200 min·d for 12 wk, and control rats were taken into water for 5 min·d. After the training period, both groups remained sedentary for 8 wk. We performed echocardiography at weeks 12 and 20 to investigate the development and regression of exercise-induced structural changes. LV pressure-volume analysis was performed to calculate cardiac functional parameters. LV samples were harvested for histological examination.

RESULTS

Echocardiography showed robust LV hypertrophy after completing the training protocol (LV mass index = 2.61 ± 0.08 DEx vs 2.04 ± 0.04 g·kg DCo, P < 0.05). This adaptation regressed after detraining (LV mass index = 2.01 ± 0.03 vs 1.97 ± 0.05 g·kg, n.s.), which was confirmed by postmortem measured heart weight and histological morphometry. After the 8-wk-long detraining period, a regression of the previously described exercise-induced cardiac functional alterations was observed (DEx vs DCo): stroke volume (SV; 144.8 ± 9.0 vs 143.9 ± 9.6 μL, P = 0.949), active relaxation (τ = 11.5 ± 0.3 vs 11.3 ± 0.4 ms, P = 0.760), contractility (preload recruitable stroke work = 69.5 ± 2.7 vs 70.9 ± 2.4 mm Hg, P = 0.709), and mechanoenergetic (mechanical efficiency = 68.7 ± 1.2 vs 69.4 ± 1.8, P = 0.742) enhancement reverted completely to control values. Myocardial stiffness remained unchanged; moreover, no fibrosis was observed after the detraining period.

CONCLUSION

Functional consequences of exercise-induced physiological LV hypertrophy completely regressed after 8 wk of deconditioning.

Physical training promotes similar effects to the blockade of angiotensin-converting enzyme on the cardiac morphology and function in old female rats subjected to premature ovarian failure

We investigated the effects of angiotensin-converting enzyme (ACE) inhibition and aerobic physical training on the heart of old female rats (82-wk-old) submitted to premature ovarian failure (10-wk.-old). We used different approaches: morphology and function by echocardiography, reactivity of the coronary bed and left ventricular contractibility (Langendorff Technique). Female Wistar ovariectomized (OVX) rats (n=42) were assigned to one of four groups: OVX, vehicle treated only; OVX-EM, Enalapril Maleate only (EM, 10mg·kg^-1·d^-1); OVX-T, aerobic trained only; and OVX-EMT, treated with Enalapril Maleate and aerobic trained. Both Enalapril Maleate treatment and aerobic training were done in the last 20weeks of the experimental protocol. When compared to the OVX group, the OVX-EM group showed lower values of wall thickness and left ventricular (LV) mass, lower values of coronary bed reactivity and reduced maximum response of LV contractility to dobutamine, while the OVX-T group showed lower values of LV wall thickness, increase in end-systolic volume, reduced maximum response of LV contractility to dobutamine, and left intraventricular pressure due to increased flow. The combination of treatments (EM and aerobic physical training) did not promote additional important effects on the parameters evaluated. Our results suggest similar beneficial effects of physical training and EM treatment on the morphology and cardiac function in old female rats submitted to premature ovarian failure. Although the causes of these benefits are still unknown, both treatments have promoted a decrease in cardiac contractility, and the reduced β1-adrenergic sensitivity suggests that both treatments may attenuate the sympathetic effect on the heart.

The effects of detraining and training on adipose tissue lipid droplet in obese mice after chronic high-fat diet

Background

It is well known that exercise promotes lipolysis by stimulating the lipid droplet (LD) signaling pathway. However, few studies have been conducted to examine the effect of detraining with high fat diet (HFD) and training effects after long-term HFD. Here, we investigated the effect of detraining and training on adipose tissue LD pathway in diet-induced obese mice after continuous HFD.

Methods

Seventy male C57BL/6 mice were randomly assigned into a Normal diet + Sedentary group (ND, n = 10) or a High-fat diet + Sedentary group (HF, n = 50); in the HF group, obesity was induced by a 45% fat chow for six weeks. For the subsequent eight weeks, the HF group was randomly subdivided into an HF (n = 30) or an HF + training group (HFT, n = 20), and the HFT group was subjected to treadmill training while on an HFD. Following this eight-week period, the HFT group stopped exercising (HFT-DT group, n = 10), and the mice in the HF group were randomly subdivided into an HF (n = 10) or an HF + training group (HF-T, n = 10). After training and detraining, abdominal visceral fat was obtained and analyzed by histological staining and western blot.

Results

Treadmill exercise decreased body weight and fat mass (P <0.05), and increased the levels of PKA, perilipin1, CGI-58, ATGL, and HSL (P <0.05) after eight weeks of training. Following eight weeks of detraining, the levels of PKA and HSL were decreased (P <0.05); however, exercise after chronic HFD increased the levels of PKA, perilipin1, CGI-58, ATGL, and HSL (P <0.05), and decreased body weight and fat mass (P <0.05).

Conclusions

Regardless of dietary restrictions, exercise is an effective treatment for obesity, owing to the regulation of LD signaling proteins. Moreover, the effects of regular exercise after chronic HFD were similar to those of exercise in the absence of HFD. Therefore, although obesity is induced by chronic HFD, exercise without dietary change is sufficiently effective for obesity treatment regardless of the preceding HFD period.

Association of Exercise Training with Tobacco Smoking Prevents Fibrosis but has Adverse Impact on Myocardial Mechanics

INTRODUCTION

There was no data for cardiac repercussion of exercise training associated with tobacco smoking. This issue is interesting because some smoking people can be enrolled in an exercise-training program. Thus, we evaluated swimming training effects on the function and structural myocardial in rats exposed to tobacco smoking.

METHODS

Male Wistar rats were assigned to one of four groups: C, untrained rats without exposure to tobacco smoking; E, exercised rats without exposure to tobacco smoking; CS, untrained rats exposed to tobacco smoking; ECS, exercised rats exposed to tobacco smoking. Rats swam five times a week twice daily (60min per session) for 8 weeks. Before each bout exercise, rats breathed smoke from 20 cigarettes for 60min. Twenty-four hours after the last day of the protocol, papillary muscles were isolated for in vitro analysis of myocardial mechanics. The myocardial mass and nuclear cardiomyocyte volume were used as hypertrophy markers, and collagen content was determined by picrosirius red staining.

RESULTS

There was a well-pronounced myocardial hypertrophic effect for two interventions. The exercise blunted myocardial collagen increases induced by tobacco smoking. However, exercise and tobacco-smoking association was deleterious to myocardial performance. Thereby, in vitro experiments with papillary muscles contracting in isometric showed impairment myocardial inotropism in exercised rats exposed to tobacco smoking.

CONCLUSIONS

This work presents novel findings on the role of exercise training on cardiac remodeling induced by tobacco smoking. Although exercise has mitigated tissue fibrosis, their association with tobacco smoking exacerbated hypertrophy and in vitro myocardial dysfunction.

IMPLICATIONS

This is first study to show that the association of an aerobic exercise training with tobacco smoking intensifies the phenotype of pathological cardiac hypertrophy. Therefore, the combination of interventions resulted in exacerbated myocardial hypertrophy and contractility dysfunction. These findings have significant clinical implication because some smoking people can be enrolled in an exercise-training program.

Coupling of myocardial stress resistance and signalling to voluntary activity and inactivity

AIMS

We examined coupling of myocardial ischaemic tolerance to physical activity and inactivity, and whether this involves modulation of survival (AKT, AMPK, ERK1/2, HSP27, EGFR) and injury (GSK3β) proteins implicated in ischaemic preconditioning and calorie restriction.

METHODS

Proteomic modifications were assessed in ventricular myocardium, and tolerance to 25-min ischaemia in ex vivo perfused hearts from C57Bl/6 mice subjected to 14-day voluntary activity in running-naïve animals (Active); 7 days of subsequent inactivity (Inactive); brief (day 3) restoration of running (Re-Active); or time-matched inactivity.

RESULTS

Active mice increased running speed and distance by 75-150% over 14 days (to ~40 m min(-1) and 10 km day(-1) ), with Active hearts resistant to post-ischaemic dysfunction (40-50% improvements in ventricular pressure development, diastolic pressure and dP/dt). Cardioprotection was accompanied by ~twofold elevations in AKT, AMPK, HSP27 and GSK3β phosphorylation and EGFR expression. Ischaemic tolerance was reversed in Inactive hearts, paralleling reduced EGFR expression and GSK3β and ERK1/2 phosphorylation (AKT, AMPK, HSP27 phosphorylation unaltered). Running characteristics, ischaemic tolerance, EGFR expression and GSK3β phosphorylation returned to Active levels within 1-3 days of restored activity (without changes in AKT, AMPK or HSP27 phosphorylation). Transcriptional responses included activity-dependent Anp induction vs. Hmox1 and Sirt3 suppression, and inactivity-dependent Adora2b induction.

CONCLUSIONS

Data confirm the sensitive coupling of ischaemic tolerance to activity: voluntary running induces cardioprotection that dissipates within 1 week of inactivity yet recovers rapidly upon subsequent activity. While exercise in naïve animals induces a molecular profile characteristic of preconditioning/calorie restriction, only GSK3β and EGFR modulation consistently parallel activity- and inactivity-dependent ischaemic tolerance.

Detraining in pregnancy and/or lactation modulates neuropeptidergic hypothalamic systems in offspring mice

Manipulations in metabolic parameters during pregnancy/lactation can impact the development of short- and long-term energy control mechanisms, which are mainly modulated by neural and hormonal inputs to the hypothalamus. Thus, we tested how mice training and detraining during pregnancy and lactation affect hypothalamus gene expression and change biometric and metabolic profiles of the offspring. Three-month-old female Swiss mice were submitted to an 8-week exercise program (swimming 5 times/week, 1 h/day). Following this physical exercise protocol, these conditioned animals and the control group were submitted to matting. After pregnancy verification, the animals were distributed into four groups: training during pregnancy and lactation (T); detraining after pregnancy confirmation (DP); detraining during lactation (DL); and control (CT), without interventions. After weaning, the offspring of the four groups were derived into these as follows: TO, DPO, DLO, and CTO, respectively. The body weight was lower in conditioned females compared to control at weeks 4-8 of the exercise regimen. No statistical difference in dam's body weight was observed during pregnancy. Related to offspring, at post-natal day 90, the animals were euthanized and DPO and DLO showed decrease in Npy and Cart expression in hypothalamus, and DLO also had increased Lep gene expression in white adipose tissue. Additionally, DPO showed increase in plasma triglycerides levels, total liver weight, and decrease in brown adipose tissue compared to CTO. Together, these results support that detraining during critical periods of development leads to altered gene expression in hypothalamic neuropeptidergic systems.

Overtraining does not induce oxidative stress and inflammation in blood and heart of rats

The aim of our research was to evaluate the changes in levels of cytokines and redox state parameters in blood and isolated heart of rats subjected to different swimming protocols. Rats were divided into 3 groups: 1) controls, 2) moderately trained rats that during all 12 weeks swam 1 h/day, 5 days/week, and 3) overtrained rats that in 10(th) week swam twice, 11(th) week 3 times, and in 12(th) week 4 times a day for 1 h. After sacrificing, blood from jugular vein was collected, and the heart excised and perfused on a Langendorff apparatus. Samples of the coronary effluent were collected during coronary autoregulation. Levels of superoxide anion radical (O(2)(-)), hydrogen peroxide (H(2)O(2)), nitric oxide (NO) and thiobarbituric acid reactive substances (TBARS) were measured in plasma and coronary effluent, while reduced glutathione (GSH), activities of superoxide dismutase (SOD) and catalase (CAT) were measured in erythrocytes. Venous blood was also used for interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) determination. Moderate training protocol induced the decrease of TBARS in plasma, while both training protocols induced the decrease of O(2)(-) and H(2)O(2) in coronary effluent. There was no significant difference in levels of cytokines between groups. The results of study add evidence about beneficial effects of moderate-intensity training on blood and cardiac redox state of rats, and furthermore, shows that exercising frequently, if the intensity stays within moderate range, may not have detrimental effects.

Effects of anaerobic exercise and detraining on the caspase-3 expression of rat ventricular cardiomyocyte

Background: Anaerobic physical exercise is a high intensity physical exercise performed in a short time. This exercise can stimulate apoptosis in left ventricular cardiomyocytes. The aim of this study is to analyze the apoptosis of cardiomyocytes after anaerobic exercise and detraining.Methods: Thirty two wistar rats Ratus Novergicus 250-350 grams (8-10 weeks old) were divided into the following groups (n = 4) and given naerobic physical exercise four and 12 weeks (group Exc-4, Exc-12) and anaerobic exercise followed by four weeks of detraining (Exc-4-D, Exc-12-D). The control groups were only observed in the same period (group CTL-4, CTL-12, CTL-4-D, CTL-12-D). At the end of observation, the rats were sacrificed and examination of the expression of caspase-3 as an indicator of apoptosis was done using immunohistochemical staining. Data were analyzed with ANOVA test.Results: An increase in expression of caspase-3 in the group Exc-4 (72.03%) compared to the CTL-4 (27.22%), (p < 0,001); and Exc-12 (79.30%) compared to the CTL-12 (30.53%) (p = 0.027). Detraining process showed a significant decline Capase-3 expression (31.12% in exc-4-D and 30.44% in the exc-12-D).Conclusion: Anaerobic physical exercise can increase apoptosis in rat left ventricle cardiomyocyte characterized by increased expression of caspase-3. Detraining can improve heart condition characterized by decreased expression of caspase-3. 

Cardiac adaptations from 4 weeks of intensity-controlled vigorous exercise are lost after a similar period of detraining

Intensity-controlled (relative to VO_2max) treadmill exercise training in adult rats results in the activation and ensuing differentiation of endogenous c-kit^pos cardiac stem/progenitor cells (eCSCs) into newly formed cardiomyocytes and capillaries. Whether these training-induced adaptations persist following detraining is undetermined. Twelve male Wistar rats (∼230 g) were exercised at 80–85% of their VO_2max for 30 min day⁻¹, 4 days week⁻¹ for 4 weeks (TR;n = 6), followed by 4 weeks of detraining (DTR; n = 6). Twelve untrained rats acted as controls (CTRL). Exercise training significantly enhanced VO_2max (11.34 mL kg⁻¹ min⁻¹) and wet heart weight (29%) above CTRL (P < 0.05). Echocardiography revealed that exercise training increased LV mass (∼32%), posterior and septal wall thickness (∼15%), ejection fraction and fractional shortening (∼10%) compared to CTRL (P < 0.05). Cardiomyocyte diameter (17.9 ± 0.1 μm vs. 14.9 ± 0.6 μm), newly formed (BrdU^pos/Ki67^pos) cardiomyocytes (7.2 ± 1.3%/1.9 ± 0.7% vs. 0.2 ± 0.1%/0.1 ± 0.1%), total cardiomyocyte number (45.6 ± 0.6 × 10⁶ vs. 42.5 ± 0.4 × 10⁶), c-kit^pos eCSC number (884 ± 112 per 10⁶ cardiomyocytes vs. 482 ± 132 per 10⁶ cardiomyocytes), and capillary density (4123 ± 227 per mm² vs. 2117 ± 118 per mm²) were significantly greater in the LV of trained animals (P < 0.05) than CTRL. Detraining removed the stimulus for c-kit^pos eCSC activation (640 ± 98 per 10⁶ cardiomyocytes) and resultant cardiomyocyte hyperplasia (0.4 ± 0.3% BrdU^pos/0.2 ± 0.2% Ki67^pos cardiomyocytes). Capillary density (3673 ± 374 per mm²) and total myocyte number (44.7 ± 0.5 × 10⁶) remained elevated following detraining, but cardiomyocyte hypertrophy (15.0 ± 0.4 μm) was lost, resulting in a reduction of anatomical (wall thickness ∼4%; LV mass ∼10% and cardiac mass ∼8%, above CTRL) and functional (EF & FS ∼2% above CTRL) parameters gained through exercise training. These findings demonstrate that cardiac adaptations, produced by 4 weeks of intensity-controlled exercise training are lost after a similar period of detraining.

Treadmill exercise training prevents myocardial mechanical dysfunction induced by androgenic-anabolic steroid treatment in rats

Elevated concentrations of testosterone and its synthetic analogs may induce changes in cardiovascular function. However, the effects of the combination of anabolic/androgenic steroid (AAS) treatment and exercise training on systolic and diastolic cardiac function are poorly understood. In the present study, we aimed to investigate the effects of low-dose steroid treatment (stanozolol) on cardiac contractile parameters when this steroid treatment was combined with exercise training in rats and the effects of chronic steroid treatment on the Frank-Starling (length-tension curves) relationship. Male Wistar rats were randomly assigned to one of four groups: U (untrained), US (untrained and treated with stanozolol 5 mg/kg/week), T (trained, 16 m/min/1 h) and TS (trained and treated with stanozolol 5 mg/kg/week). Continuous exercise training was conducted 5 days/week for 8 consecutive weeks. The speed of the treadmill was gradually increased to a final setting of 16 m/min/1 h. Experiments were divided into two independent series: 1) central hemodynamic analysis for mean arterial blood pressure (MAP) and cardiac output (CO) measurements and 2) isolated papillary muscle preparation in Krebs solution. Stanozolol treatment significantly increased the MAP and the heart size in untrained and trained rats (U 113±2; T 106±2; US 138±8 and TS 130±7 mmHg). Furthermore, stanozolol significantly decreased developed tension and dT/dt (maximal and minimal) in U rats. However, the developed tension was completely restored by training. The Frank/Starling relationship was impaired in rats treated with stanozolol; however, again, training completely restored diastolic function. Taken together, the present data suggest that AAS treatment is able to decrease cardiac performance (systolic and diastolic functions). The combination of stanozolol and physical training improved cardiac performance, including diastolic and systolic functions, independent of changes in central hemodynamic parameters. Therefore, changes in ventricular myocyte calcium transients may play a cardioprotective role.

Rat model of exercise-induced cardiac hypertrophy: hemodynamic characterization using left ventricular pressure-volume analysis

Long-term exercise training is associated with characteristic structural and functional changes of the myocardium, termed athlete's heart. Several research groups investigated exercise training-induced left ventricular (LV) hypertrophy in animal models; however, only sporadic data exist about detailed hemodynamics. We aimed to provide functional characterization of exercise-induced cardiac hypertrophy in a rat model using the in vivo method of LV pressure-volume (P-V) analysis. After inducing LV hypertrophy by swim training, we assessed LV morphometry by echocardiography and performed LV P-V analysis using a pressure-conductance microcatheter to investigate in vivo cardiac function. Echocardiography showed LV hypertrophy (LV mass index: 2.41 ± 0.09 vs. 2.03 ± 0.08 g/kg, P < 0.01), which was confirmed by heart weight data and histomorphometry. Invasive hemodynamic measurements showed unaltered heart rate, arterial pressure, and LV end-diastolic volume along with decreased LV end-systolic volume, thus increased stroke volume and ejection fraction (73.7 ± 0.8 vs. 64.1 ± 1.5%, P < 0.01) in trained versus untrained control rats. The P-V loop-derived sensitive, load-independent contractility indexes, such as slope of end-systolic P-V relationship or preload recruitable stroke work (77.0 ± 6.8 vs. 54.3 ± 4.8 mmHg, P = 0.01) were found to be significantly increased. The observed improvement of ventriculoarterial coupling (0.37 ± 0.02 vs. 0.65 ± 0.08, P < 0.01), along with increased LV stroke work and mechanical efficiency, reflects improved mechanoenergetics of exercise-induced cardiac hypertrophy. Despite the significant hypertrophy, we observed unaltered LV stiffness (slope of end-diastolic P-V relationship: 0.043 ± 0.007 vs. 0.040 ± 0.006 mmHg/μl) and improved LV active relaxation (τ: 10.1 ± 0.6 vs. 11.9 ± 0.2 ms, P < 0.01). According to our knowledge, this is the first study that provides characterization of functional changes and hemodynamic relations in exercise-induced cardiac hypertrophy.

Exercise attenuates renal dysfunction with preservation of myocardial function in chronic kidney disease

Previous studies have suggested that exercise improves renal and cardiac functions in patients with chronic kidney disease. The aim of this study was to evaluate the effects of long-term aerobic swimming exercise with overload on renal and cardiac function in rats with 5/6 nefrectomy (5/6Nx). Eight Wistar rats were placed into 4 groups: Control (C), Control+Exercise (E), Sedentary 5/6Nx (NxS) and 5/6Nx+Exercise (NxE). The rats were subjected to swimming exercise sessions with overload for 30 min five days per week for five weeks. Exercise reduced the effect of 5/6Nx on creatinine clearance compared to the NxS group. In addition, exercise minimized the increase in mean proteinuria compared to the NxS group (96.9±10.0 vs. 51.4±9.9 mg/24 h; p<0.05). Blood pressure was higher in the NxS and NxE groups compared to the C and E groups (216±4 and 178±3 vs. 123±2 and 124±2 mm Hg, p<0.05). In the 200 glomeruli that were evaluated, the NxS group had a higher sclerosis index than did the NxE group (16% vs. 2%, p<0.05). Echocardiography demonstrated a higher anterior wall of the left ventricle (LV) in diastole in the NxS group compared with the C, E and NxE groups. The NxS group also had a higher LV posterior wall in diastole and systole compared with the E group. The developed isometric tension in Lmax of the heart papillary muscle was lower in the NxS group compared with the C, E and NxE groups. These results suggested that exercise in 5/6Nx animals might reduce the progression of renal disease and lessen the cardiovascular impact of a reduction in renal mass.

Detraining differentially preserved beneficial effects of exercise on hypertension: effects on blood pressure, cardiac function, brain inflammatory cytokines and oxidative stress

Aims

This study sought to investigate the effects of physical detraining on blood pressure (BP) and cardiac morphology and function in hypertension, and on pro- and anti-inflammatory cytokines (PICs and AIC) and oxidative stress within the brain of hypertensive rats.

Methods and Results

Hypertension was induced in male Sprague-Dawley rats by delivering AngiotensinII for 42 days using implanted osmotic minipumps. Rats were randomized into sedentary, trained, and detrained groups. Trained rats underwent moderate-intensity exercise (ExT) for 42 days, whereas, detrained groups underwent 28 days of exercise followed by 14 days of detraining. BP and cardiac function were evaluated by radio-telemetry and echocardiography, respectively. At the end, the paraventricular nucleus (PVN) was analyzed by Real-time RT-PCR and Western blot. ExT in AngII-infused rats caused delayed progression of hypertension, reduced cardiac hypertrophy, and improved diastolic function. These results were associated with significantly reduced PICs, increased AIC (interleukin (IL)-10), and attenuated oxidative stress in the PVN. Detraining did not abolish the exercise-induced attenuation in MAP in hypertensive rats; however, detraining failed to completely preserve exercise-mediated improvement in cardiac hypertrophy and function. Additionally, detraining did not reverse exercise-induced improvement in PICs in the PVN of hypertensive rats; however, the improvements in IL-10 were abolished.

Conclusion

These results indicate that although 2 weeks of detraining is not long enough to completely abolish the beneficial effects of regular exercise, continuing cessation of exercise may lead to detrimental effects.

Akt and MAPK signaling mediate pregnancy-induced cardiac adaptation

Although the signaling pathways underlying exercise-induced cardiac adaptation have been extensively studied, little is known about the molecular mechanisms that result in the response of the heart to pregnancy. The objective of this study was to define the morphological, functional, and gene expression patterns that define the hearts of pregnant mice, and to identify the signaling pathways that mediate this response. Mice were divided into three groups: nonpregnant diestrus control, midpregnancy, and late pregnancy. Both time points of pregnancy were associated with significant cardiac hypertrophy. The prosurvival signaling cascades of Akt and ERK1/2 were activated in the hearts of pregnant mice, while the stress kinase, p38, was decreased. Given the activation of Akt in pregnancy and its known role in cardiac hypertrophy, the hypertrophic response to pregnancy was tested in mice expressing a cardiac-specific activated (myristoylated) form of Akt (myrAkt) or a cardiac-specific constitutively active (antipathologic hypertrophic) form of its downstream target, glycogen synthase kinase 3β (caGSK3β). The pregnancy-induced hypertrophic responses of hearts from these mice were significantly attenuated. Finally, we tested whether pregnancy-associated sex hormones could induce hypertrophy and alter signaling pathways in isolated neonatal rat ventricular myocytes (NRVMs). In fact, progesterone, but not estradiol treatment increased NRVM cell size via phosphorylation of ERK1/2. Inhibition of MEK1 effectively blocked progesterone-induced cellular hypertrophy. Taken together, our study demonstrates that pregnancy-induced cardiac hypertrophy is mediated by activation of Akt and ERK1/2 pathways.

The effects of detraining on blood adipokines and antioxidant enzyme in Korean overweight children

The present study examined the change to clarify the effects of detraining on the concentration of lipid profiles, serum adipokines and antioxidant enzyme gene expression in Korean overweight children. The subjects were normal children (n = 19) and obese children (n = 20) who were further subdivided into the overweight training (OT) group (n = 10) and the overweight detraining (OD) group (n = 10). Maximal oxygen uptake (VO(2)max); body composition; lipid profiles (TG, TC); adipokines (adiponectin and leptin); antioxidants (blood and gene expressions SOD and GPX) were measured before, 12 weeks, and 24 weeks after the exercise program. Body mass index (BMI) and %fat were significantly higher in the OD group only. However, waist hip ration (WHR) and systolic blood pressure (SBP) were significantly decreased in the OT group. TG was significantly decreased in the OT group. There was a significant difference in TG level between the two groups. Besides, adiponectin was significantly increased in both the OT group and the OD group. Furthermore, leptin was significantly decreased in the OT group. There was a significant difference in leptin level between the two groups. In training groups, the expression of SOD was significantly increased after a 12- and 24-week period (p < 0.05). However, detraining group was significantly increased after a 12-week only (p < 0.05). In addition, GPX was significantly increased after a 24-week only in the training group (p < 0.05). Thus, detraining showed that negative effected on body composition and lipid profiles and maintained of uniform period on adipokines and antioxidant enzyme the protein and expression.

American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise

The purpose of this Position Stand is to provide guidance to professionals who counsel and prescribe individualized exercise to apparently healthy adults of all ages. These recommendations also may apply to adults with certain chronic diseases or disabilities, when appropriately evaluated and advised by a health professional. This document supersedes the 1998 American College of Sports Medicine (ACSM) Position Stand, "The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults." The scientific evidence demonstrating the beneficial effects of exercise is indisputable, and the benefits of exercise far outweigh the risks in most adults. A program of regular exercise that includes cardiorespiratory, resistance, flexibility, and neuromotor exercise training beyond activities of daily living to improve and maintain physical fitness and health is essential for most adults. The ACSM recommends that most adults engage in moderate-intensity cardiorespiratory exercise training for ≥30 min·d on ≥5 d·wk for a total of ≥150 min·wk, vigorous-intensity cardiorespiratory exercise training for ≥20 min·d on ≥3 d·wk (≥75 min·wk), or a combination of moderate- and vigorous-intensity exercise to achieve a total energy expenditure of ≥500-1000 MET·min·wk. On 2-3 d·wk, adults should also perform resistance exercises for each of the major muscle groups, and neuromotor exercise involving balance, agility, and coordination. Crucial to maintaining joint range of movement, completing a series of flexibility exercises for each the major muscle-tendon groups (a total of 60 s per exercise) on ≥2 d·wk is recommended. The exercise program should be modified according to an individual's habitual physical activity, physical function, health status, exercise responses, and stated goals. Adults who are unable or unwilling to meet the exercise targets outlined here still can benefit from engaging in amounts of exercise less than recommended. In addition to exercising regularly, there are health benefits in concurrently reducing total time engaged in sedentary pursuits and also by interspersing frequent, short bouts of standing and physical activity between periods of sedentary activity, even in physically active adults. Behaviorally based exercise interventions, the use of behavior change strategies, supervision by an experienced fitness instructor, and exercise that is pleasant and enjoyable can improve adoption and adherence to prescribed exercise programs. Educating adults about and screening for signs and symptoms of CHD and gradual progression of exercise intensity and volume may reduce the risks of exercise. Consultations with a medical professional and diagnostic exercise testing for CHD are useful when clinically indicated but are not recommended for universal screening to enhance the safety of exercise.

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.

Exercise training attenuates acute hyperalgesia in streptozotocin-induced diabetic female rats

OBJECTIVES

We investigated the effects of chronic (eight weeks) low-to moderate-intensity swimming training on thermal pain sensitivity in streptozotocin-induced diabetic female rats.

METHODS

Female Wistar rats (n = 51) were divided into the following groups: trained streptozotocin-induced diabetic rats [hyperglycemic trained (HT)], sedentary streptozotocin-induced diabetic rats [hyperglycemic sedentary (HS)], normoglycemic trained rats (NT) and normoglycemic sedentary rats (NS). Diabetes was induced by a single injection of streptozotocin (50 mg/kg, i.p.). One day after the last exercise protocol (60 min/day, five days/week for eight weeks) in the trained groups or after water stress exposure (ten min/twice a week) in the sedentary groups, the rats were subjected to a hot plate test.

RESULTS

After eight weeks of swimming training, streptozotocin-induced diabetic rats presented a significantly lower body mass (trained: 219.5 ± 29 g, sedentary: 217.8 ± 23 g) compared with the normoglycemic groups (trained: 271 ± 24 g, sedentary: 275.7 ± 32 g). Interestingly, we did not find differences in blood glucose levels (mg/dl) between the trained and sedentary groups of the hyperglycemic or normoglycemic rats (HT: 360.2 ± 66.6, HS: 391.7 ± 66.7, NT: 83.8 ± 14.0, NS: 77.5 ± 10.1). In the hot plate test, the rats from the HT group presented a significantly lower latency than the other rats (HT: 11.7 ± 7.38 s, HS: 7.02 ± 7.38 s, NT: 21.21 ± 7.64 s, NS: 22.82 ± 7.82 s).

CONCLUSION

Low-to-moderate swimming training for a long duration reduces thermal hyperalgesia during a hot plate test in streptozotocin-induced diabetic female rats.

Exercise training and detraining modify the morphological and mechanical properties of single cardiac myocytes obtained from spontaneously hypertensive rats

We determined the effects of exercise training and detraining on the morphological and mechanical properties of left ventricular myocytes in 4-month-old spontaneously hypertensive rats (SHR) randomly divided into the following groups: sedentary for 8 weeks (SED-8), sedentary for 12 weeks (SED-12), treadmill-running trained for 8 weeks (TRA, 16 m/min, 60 min/day, 5 days/week), and treadmill-running trained for 8 weeks followed by 4 weeks of detraining (DET). At sacrifice, left ventricular myocytes were isolated enzymatically, and resting cell length, width, and cell shortening after stimulation at a frequency of 1 Hz (~25°C) were measured. Cell length was greater in TRA than in SED-8 (161.30 ± 1.01 vs 156.10 ± 1.02 μm, P < 0.05, 667 vs 618 cells, respectively) and remained larger after detraining. Cell width and volume were unaffected by either exercise training or detraining. Cell length to width ratio was higher in TRA than in SED-8 (8.50 ± 0.08 vs 8.22 ± 0.10, P < 0.05) and was maintained after detraining. Exercise training did not affect cell shortening, which was unchanged with detraining. TRA cells exhibited higher maximum velocity of shortening than SED-8 (102.01 ± 4.50 vs 82.01 ± 5.30 μm/s, P < 0.05, 70 cells per group), with almost complete regression after detraining. The maximum velocity of relengthening was higher in TRA cells than in SED-8 (88.20 ± 4.01 vs70.01 ± 4.80 μm/s, P < 0.05), returning to sedentary values with detraining. Therefore, exercise training affected left ventricle remodeling in SHR towards eccentric hypertrophy, which remained after detraining. It also improved single left ventricular myocyte contractile function, which was reversed by detraining.

The beneficial effects of exercise in rodents are preserved after detraining: a phenomenon unrelated to GLUT4 expression

BACKGROUND

Although exercise training has well-known cardiorespiratory and metabolic benefits, low compliance with exercise training programs is a fact, and the harmful effects of physical detraining regarding these adaptations usually go unnoticed. We investigated the effects of exercise detraining on blood pressure, insulin sensitivity, and GLUT4 expression in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY).

METHODS

Studied animals were randomized into sedentary, trained (treadmill running/5 days a week, 60 min/day for 10 weeks), 1 week of detraining, and 2 weeks of detraining. Blood pressure (tail-cuff system), insulin sensitivity (kITT), and GLUT4 (Western blot) in heart, gastrocnemius and white fat tissue were measured.

RESULTS

Exercise training reduced blood pressure (19%), improved insulin sensitivity (24%), and increased GLUT4 in the heart (+34%); gastrocnemius (+36%) and fat (+22%) in SHR. In WKY no change in either blood pressure or insulin sensitivity were observed, but there was an increase in GLUT4 in the heart (+25%), gastrocnemius (+45%) and fat (+36%) induced by training. Both periods of detraining did not induce any change in neither blood pressure nor insulin sensitivity in SHR and WKY. One-week detraining reduced GLUT4 in SHR (heart: -28%; fat: -23%) and WKY (heart: -19%; fat: -22%); GLUT4 in the gastrocnemius was reduced after a 2-week detraining (SHR: -35%; WKY: -25%). There was a positive correlation between GLUT4 (gastrocnemius) and the maximal velocity in the exercise test (r = 0.60, p = 0.004).

CONCLUSIONS

The study findings show that in detraining, despite reversion of the enhanced GLUT4 expression, cardiorespiratory and metabolic beneficial effects of exercise are preserved.