Exercise-induced Myocardial Injury Research Articles

Protective function of albiflorin against ferroptosis in exhaustive exerciseinduced myocardial injury via the AKT/Nrf2/HO-1 signaling.

It has been reported that exhaustive exercise (EE) causes myocyte injury, and eventually damages the function of the myocardia. Albiflorin (AF) has anti-inflammatory, antioxidant, and anti-apoptosis effects. In this study, we determined whether AF could mitigate the EE-induced myocardial injury and research the potential mechanisms. The rat model of EE was built by forced treadmill running method. Rats were intraperitoneally injected with AF before EE once daily for one week. The relative factors levels were examined by commercial kits. The apoptosis was appraised using a TdT-mediated dUTP nick end labeling assay kit. The ACSL4, GPX4, Nrf2, pAKT/AKT, and HO-1 contents were assessed by western blot. AF lessened EE-induced cardiac myocytes ischemic/hypoxic injury and reduced the contents of myocardial injury biomarkers in the serum. AF lessened EE-induced cardiac myocyte apoptosis, inflammatory response, oxidative stress, and ferroptosis in myocardial tissues. However, the influences of AF were overturned by the co-treatment of AF and LY294002. AF activated the AKT/Nrf2/HO-1 signaling pathway in myocardial tissues in vivo. AF could curb cardiac myocytes ferroptosis, thus diminishing the EE-induced myocardial injury through activating the AKT/Nrf2/HO-1 cascade.

Exercise preconditioning promotes myocardial GLUT4 translocation and induces autophagy to alleviate exhaustive exercise-induced myocardial injury in rats.

Exercise preconditioning (EP) is a line of scientific inquiry into the short-term biochemical mediators of cardioprotection in the heart. This study examined the involvement of autophagy induced by energy metabolism in myocardial remodelling by EP and myocardial protection. A total of 120 healthy male Sprague Dawley (SD) rats were randomly divided into six groups. Plasma cTnI, HBFP staining and electrocardiographic indicators were examined in the context of myocardial ischemic/hypoxic injury and protection. Western blotting and fluorescence double labelling were used to investigate the relationship between energy metabolism and autophagy in EP-resistant myocardial injury caused by exhaustive exercise. Compared with those in the C group, the levels of myocardial ischemic/hypoxic injury were significantly increased in the EE group. Compared with those in the EE group, the levels of myocardial ischemic/hypoxic injury were significantly decreased in the EEP + EE and LEP + EE groups. Compared with that in the EE group, the level of GLUT4 in the sarcolemma was significantly increased, and the colocalization of GLUT4 with the sarcolemma was significantly increased in the EEP + EE and LEP + EE groups (P < 0.05). LC3-II and LC3-II/LC3-I levels of the EEP + EE group were significantly elevated compared with those in the EE group (P < 0.05). The levels of p62 were significantly decreased in the EEP + EE and LEP + EE groups compared with the EE group (P < 0.05). EP promotes GLUT4 translocation and induced autophagy to alleviate exhaustive exercise-induced myocardial ischemic/hypoxic injury.

Rhodiola pre-conditioning reduces exhaustive exercise-induced myocardial injury of insulin resistant mice

Myocardial injury reduction and recovery under acute cardiac stress are adversely impacted by insulin resistance (IR). We previously demonstrated that Rhodiola improved cardiac anti-stress capacity in mice. Thus, this study focuses on the preventive efficacy of Rhodiola on exhaustive exercise (EE)-induced myocardial injury of IR mice. An 8-week high-fat diet (HFD) model of IR mice was established. Rhodiola was administrated by garaging. After the 8-week intervention, half of the mice performed EE to simulate acute cardiac stress, and determine myocardial injury; The remaining mice were sacrificed following fasting to assess metabolic disorder. We found myocardial injury induced by EE in IR mice was worse and was alleviated by Rhodiola pre-conditioning. Further, the nuclear factor erythroid 2-related factor 2 (Nrf2)-related antioxidant system was impaired by HFD, while mitochondrial dynamic fusion and fission were activated by HFD as a physiological protective compensation. The Rhodiola administration rescued Nrf2 impairment and further facilitated mitochondrial fusion and fission. All these results indicate that Rhodiola is a potential treatment for the prevention of cardiac events in type 2 diabetes mellitus and metabolic syndrome patients, and the Nrf2-related antioxidant activity and mitochondrial dynamics are the proposed mechanisms.

Novel insights into exhaustive exercise-induced myocardial injury: Focusing on mitochondrial quality control.

Regular moderate-intensity exercise elicits benefit cardiovascular health outcomes. However, exhaustive exercise (EE) triggers arrhythmia, heart failure, and sudden cardiac death. Therefore, a better understanding of unfavorable heart sequelae of EE is important. Various mechanisms have been postulated for EE-induced cardiac injury, among which mitochondrial dysfunction is considered the cardinal machinery for pathogenesis of various diseases. Mitochondrial quality control (MQC) is critical for clearance of long-lived or damaged mitochondria, regulation of energy metabolism and cell apoptosis, maintenance of cardiac homeostasis and alleviation of EE-induced injury. In this review, we will focus on MQC mechanisms and propose mitochondrial pathophysiological targets for the management of EE-induced myocardial injury. A thorough understanding of how MQC system functions in the maintenance of mitochondrial homeostasis will provide a feasible rationale for developing potential therapeutic interventions for EE-induced injury.

Protective effect and mechanism of cannabidiol on myocardial injury in exhaustive exercise training mice

Cannabinoid diphenol (CBD) is a non-toxic main component extracted from cannabis, which has the effects of anti-inflammatory, anti-apoptosis and anti-oxidative stress. In recent years, exercise-induced myocardial injury has become a research hotspot in the field of sports medicine and sports physiology. Exercise-induced myocardial injury is closely related to oxidative stress, inflammatory response and apoptosis. However, there is no clear evidence of the relationship between CBD and exercise-induced myocardial injury. In this study, by establishing an animal model of exhaustive exercise training in mice, the protective effect of CBD on myocardial injury in mice was elaborated, and the possible molecular mechanism was discussed. After CBD intervention, the arrangement and rupture of myocardial fiber tissue and the degree of inflammatory cell infiltration were reduced, the deposition of collagen fibers in myocardial tissue decreased. CBD can also significantly inhibit cardiac hypertrophy. Meanwhile, the expression of IL-6, IL-10, TNF-α, Bax, Caspase-3, Bcl-2, MDA-5, IRE-1α, NOX-2, SOD-1, Keap1, Nrf2, HO-1, NF-κB and COX-2 was recovered to normal. In addition, after CBD intervention, the protein expression of Keap1 was down-regulated, the translocation of Nrf2 from the cytoplasm to the nucleus was significantly increased, then the transcriptional activity was increased, and the expression of the downstream HO-1 antioxidant protein was increased, indicating that CBD may improve the cardiac function of exhaustive exercise training mice by activating Keap1/Nrf2/HO-1 signaling pathway. Molecular docking results also confirmed that CBD had a good binding effect with Keap1/Nrf2/HO-1 signaling pathway proteins. In conclusion, the protective mechanism of CBD on myocardial injury in exhaustive exercise training mice may be to activate Keap1/Nrf2/HO-1 signaling pathway, and then exert anti-inflammatory, anti-apoptosis and inhibition of oxidative stress.

Pretreatment of Nicorandil Protects the Heart from Exhaustive Exercise-Induced Myocardial Injury in Rats.

Objective Nicorandil has been widely used for the treatment of angina pectoris and myocardial infarction. The purpose of this study was to investigate whether nicorandil plays a protective role in exhaustive exercise (EE)-induced myocardial injury. Methods Here, we applied the rat EE model and treated them with exercise preconditioning (EP, reported to protect the heart) or different doses of nicorandil gavage, respectively, to explore whether there are protective effects of single EP or nicorandil or a combination of both and the potential mechanism. Forty-nine male Sprague Dawley rats were randomly divided into control, EE, EP + EE, nicorandil (with low, middle, and high dose) + EE, and EP + nicorandil (middle dose) + EE. Blood samples and myocardial tissues were collected to analyze the myocardial injury-related index. Results EE induced myocardial structural damage and altered the myocardial injury markers, which were partially reversed by pretreatment of nicorandil. In addition, oxidative stress and inflammation lead to the accumulation of reactive oxygen species (ROS) products and further damage to the myocardium, while pretreatment of nicorandil reduces the oxidative stress response and inflammation. Moreover, nicorandil suppressed the myocardial apoptosis induced by EE, as indicated by a decrease of Bax and caspase-3 expression and an increase of Bcl-2 expression. Finally, the pathway in which nicorandil plays a role may be involved in the endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) pathway. Pretreatment of nicorandil increased the protein level of myocardial eNOS and NO production. Conclusion Our result demonstrated that nicorandil has protective effects in EE-induced myocardial injury with dose-dependent effects. A combination of nicorandil and EP can further improve the protective effects. Taken together, nicorandil can be potentially used as an intervention method in EE-induced myocardial injury.

Astragalus polysaccharide attenuates overexercise-induce myocardial injury via activating AMPK signaling pathway to suppress inflammation and oxidative stress.

Excessive exercise leads to myocardial injury or even sudden exercise death. For the vast sports population, appropriate physiological state is a necessary condition for exercise. The present study aims to investigate the cardioprotective effects and potent mechanism of astragalus polysaccharide (APS) treatment against the exercise-induced myocardial injury via in vitro cell-based assay and in vivo model rat. Efficacies of APS incubation on the inflammatory response and oxidative stress induced by LPS were both explored in H9c2 cells by using CCK-8 and western blotting method, respectively. Normal SD rats were randomly divided into saline-treated overexercise rat group, and APS-treated overexercise rat groups with three doses. Then long-term swimming training load cycle (8 week) were performed on these rats. Finally, the changes on body weight, myocardial morphological and injury indicators, as well as the inflammation-related proteins in overexercise-induced model rats were all assessed. Three concentrations of APS all significantly increased cell viability, and decreased the apoptosis of cardiomyocytes in LPS-treated H9c2 cells. Moreover, chronic treatment of APS at all three doses also could obviously decreased myocardial injury-related indicators. Furthermore, the histopathologic examination exhibited that the APS successfully attenuated the changes of myocardial tissues, reduced the lipid accumulation and the protein levels of IL-1β, TNF-α and NF-κB. Furthermore, the APS could activate the AMPK signaling pathway, enhance the autophagy and suppress the production of ROS. On conclusions, APS exerted the protective efficacies on overexercise-induced myocardial injury by activating the AMPK signaling pathway to increase autophagy and suppress the inflammation response, oxidative stress, apoptosis of myocardial cells.

S100A1 is Involved in Myocardial Injury Induced by Exhaustive Exercise.

Many studies have confirmed that exhaustive exercise has adverse effects on the heart by generating reactive oxygen species (ROS). S100A1 calcium-binding protein A1 (S100A1) is a regulator of myocardial contractility and a protector against myocardial injury. However, few studies have investigated the role of S100A1 in the regulation of myocardial injury induced by exhaustive exercise. In the present study, we suggested that exhaustive exercise led to increased ROS, downregulation of S100a1, and myocardial injury. Downregulation of S100a1 promoted exhaustive exercise-induced myocardial injury and overexpression of S100A1 reversed oxidative stress-induced cardiomyocyte injury, indicating S100A1 is a protective factor against myocardial injury caused by exhaustive exercise. We also found that downregulation of S100A1 promoted damage to critical proteins of the mitochondria by inhibiting the expression of Ant1, Pgc1a, and Tfam under exhaustive exercise. Our study indicated S100A1 as a potential prognostic biomarker or therapeutic target to improve the myocardial damage induced by exhaustive exercise and provided new insights into the molecular mechanisms underlying the myocardial injury effect of exhaustive exercise.

Exercise Preconditioning Promotes Autophagy to Cooperate for Cardioprotection by Increasing LC3 Lipidation-Associated Proteins.

The cardioprotection of exercise preconditioning (EP) has been well documented. EP can be divided into two phases that are the induction of exercise preconditioning (IEP) and the protection of exercise preconditioning (PEP). PEP is characterized by biphasic protection, including early exercise preconditioning (EEP) and late exercise preconditioning (LEP). LC3 lipidation-mediated autophagy plays a pivotal role in cardioprotection. This study aimed to investigate the alterations of LC3 lipidation-associated proteins during EP-induced cardioprotection against myocardial injury induced by exhaustive exercise (EE) was used in a rat model of EP. These rats were subjected to an intermittent exercise consisting of four periods, with each period including 10 min of running at 30 m/min and 0% grade (approximately 75% VO2max) followed by 10 min of intermittent rest. A model of EE-induced myocardial injury was developed by subjecting rats to a consecutive running (30 m/min, 0% grade) till exhaustion. Following EEP, the colocalization of LC3 with Atg7 was significantly increased, and LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. Following LEP, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. A group of rats were subjected to EEP followed by EE, and the co-localization of LC3 with Atg7 was significantly increased, while LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were also significantly increased. Moreover, there was a significant increase in the co-localization of LC3 with Atg7, LC3-I, LC3-II, Atg7, and Atg4B levels during LEP followed by EE. The formation of autophagosome during LEP followed by EE may have been weaker than that during EEP followed by EE due to the lower lipidation of LC3. EP may promote autophagy to maintain cell homeostasis and survival, which cooperates for cardioprotection of alleviating exhaustive exercise-induced myocardial injury by increasing LC3 lipidation-associated proteins. There is a difference between EEP and LEP in terms of the mechanisms of cardioprotection afforded by these respective conditions. The positive regulation of transcription and translation level of LC3 lipidation-associated proteins may all be involved in the mechanism of EEP and LEP, while compared with LEP, the regulation of translation level of EEP is more positively to promote autophagy.

Comparison of myocardial ischemic/hypoxic staining techniques for evaluating the alleviation of exhaustive exercise-induced myocardial injury by exercise preconditioning.

Exercise preconditioning (EP) can alleviate myocardial ischemic/hypoxic injury by inducing endogenous cardioprotection. Hematoxylin-eosin (HE), hematoxylin-basic fuchsin-picric acid (HBFP), and chromotrope-2R brilliant green (C-2R BG) staining have been used to visualize myocardial ischemic/hypoxic changes in previous EP studies, but comprehensive evaluation and comparisons of these methods are lacking. This study evaluated ischemic/hypoxic changes in adjacent myocardial sections by HE, HBFP, and C-2R BG and compared the characteristics of sections stained by these three methods to show changes associated with exercise-induced myocardial ischemic/hypoxic injury. Rats were randomly divided into four groups: control (C), exercise preconditioning (EP), exhaustive exercise (EE), and exercise preconditioning + exhaustive exercise (EP + EE). Adjacent myocardial sections were stained as described above and compared to evaluate the effects of exercise-induced myocardial ischemic/hypoxic injury. The three staining methods revealed consistent localization patterns of myocardial ischemic/hypoxic injury in all groups. Results suggest that EP can alleviate exhaustive exercise-induced myocardial ischemic/hypoxic injury, and the three staining methods are suitable for the histological study of exercise-induced myocardial ischemic/hypoxic injury and protection. HE staining is a simple procedure but is not specific for myocardial ischemic/hypoxic injury. HBFP and C-2R BG staining can be used to specifically visualize myocardial ischemic/hypoxic injury.

Is cardiac troponin elevation following strenuous exercise clinically relevant in healthy subjects?

Abstract Background Exercise causes an increase in cardiac troponin (cTn) levels. Exercise-induced myocardial injury (cTn &amp;gt; the 99th percentile) has been associated with adverse cardiovascular (CV) outcomes in older subjects with CV risk factors. The long-term clinical implications of exercise-induced cardiac troponin elevations in healthy individuals has not been determined. Purpose To assess the association between exercise-induced cardiac troponin increase above the 99th percentile and all-cause death, myocardial infarction, revascularization, sudden cardiac arrest, heart failure admission and stroke during 5-years follow-up in a large cohort of healthy recreational athletes. Methods 1002 healthy subjects that completed a 91-km bike race in 2014 were eligible. Follow-up data was available for 991 subjects (99%). High-sensitivity cardiac troponin I (cTnI) and T (cTnT) were obtained 24h prior to the race, and at 3h and 24h after the race in 2014. Results Median age was 46 (25th-75th percentile: 40–53) years at inclusion, and 776 (78%) were male. Race duration was 3.8 (3.4–4.3) hours. At 3-hours following the race 821 (82.8%) of subjects exceeded the sex-specific 99th percentile of the cTnI assay and 910 (91.8%) of the cTnT assay. At 24-hours following the race 168 (17%) of subjects exceeded the sex-specific 99th percentile of the cTnI assay and 263 (27%) of the cTnT assay. During 5 years of follow-up 12 subjects (1.2%) suffered a CV event. Exercise-induced cardiac troponin increase above the 99th percentile was not associated with increased risk of adverse CV events, neither at 3-hours nor at 24-hours following the race (Figure 1). This finding was further supported by no significant relationship between adverse CV events and cTnI or cTnT at any time-point, assessed as continuous variables. Conclusion Myocardial injury, defined as a cardiac troponin level above the 99th percentile, occurs frequently following strenuous exercise. In the present study, however, healthy subjects with cardiac troponin increase above the 99th percentile following strenuous exercise were not found to have an increased five-year risk of cardiovascular events. frequent occurrence following strenuous exercise. Figure 1 Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Stavanger University Hospital, Abbott Diagnostics

Semaglutide attenuates excessive exercise-induced myocardial injury through inhibiting oxidative stress and inflammation in rats

AimsTo investigate the protective effects and mechanism of semaglutide on exercise-induced myocardial injury. Main methodsEffects of semaglutide on lipopolysaccharide (LPS)-induced oxidative stress injuries and inflammatory response were assessed in H9c2 cell via MTT assay and Western blot. Quiet control group, over training group and three doses of semaglutide treated overtraining groups were subjected to the swimming training with increasing load for consecutive 10 weeks. Immediately after the last training, the body weight, myocardial morphological changes, injury markers and inflammatory response related proteins of the model rats were analyzed. Key findingsSemaglutide at three concentrations in LPS treated H9c2 cells significantly increased the survival rate and inhibited the apoptosis of cardiomyocytes. Moreover, semaglutide activated AMPK pathway, improve autophagy and inhibited reactive oxygen species production in LPS treated H9C2 cells. In vivo results further revealed that chronic treatment of semaglutide induced significant increase in myocardial injury markers. The pathological histology analysis results showed that semaglutide ameliorated myocardial morphological changes, reduced area of lipid accumulation and significantly decreased the expression levels of NF-κB, TNF-α and IL-1β. SignificanceSemaglutide exert the protective effects on exercise-induced cardiomyopathy by activating AMPK pathway, increasing autophagy, reducing the production of ROS and inflammation-related proteins.

Altered expression levels of autophagy-associated proteins during exercise preconditioning indicate the involvement of autophagy in cardioprotection against exercise-induced myocardial injury

Exercise has been reported to induce autophagy. We hypothesized that exercise preconditioning (EP)-related autophagy in cardiomyocytes could be attributed to intermittent ischemia–hypoxia, allowing the heart to be protected for subsequent high-intensity exercise (HE). We applied approaches, chromotrope-2R brilliant green (C-2R BG) staining and plasma cTnI levels measuring, to characterize two periods of cardioprotection after EP: early EP (EEP) and late EP (LEP). Further addressing the relationship between ischemia–hypoxia and autophagy, key proteins, Beclin1, LC3, Cathepsin D, and p62, were determined by immunohistochemical staining, western blotting, and by their adjacent slices with C-2R BG. Results indicated that exercise-induced ischemia–hypoxia is a key factor in Beclin1-dependent autophagy. High-intensity exercise was associated with the impairment of autophagy due to high levels of LC3II and unchanged levels of p62, intermittent ischemia–hypoxia by EP itself plays a key role in autophagy, which resulted in more favorable cellular effects during EEP-cardioprotection compared to LEP.

Late Exercise Preconditioning Promotes Autophagy against Exhaustive Exercise-Induced Myocardial Injury through the Activation of the AMPK-mTOR-ULK1 Pathway.

Accumulating evidence shows that the AMPK-mTOR pathway modulates autophagy via coordinated phosphorylation of ULK1. The aim of the present study was to investigate the relationship between AMPK, mTOR, and ULK1 during late exercise preconditioning (LEP), and to explore whether LEP-induced myocardial protection is related to the autophagy. The exercise preconditioning (EP) protocol was as follows: rats were instructed to for run four repeated in duration of 10 minutes (including 10 minutes rest between each period) on a treadmill. Exhaustive exercise (EE) after LEP pretreatment and administration of wortmannin (an autophagy inhibitor that suppresses Class III PI3K-kinase (PI3KC3) activity) were added to test the protective effect. Cardiac troponin I (cTnI), and transmission electron microscopy (TEM), along with hematoxylin-basic fuchsin-picric acid (HBFP) staining, were used to evaluate the myocardial ischemic-hypoxic injury and protection. Western blot was used to analyze the relationship of autophagy-associated proteins. Exhaustive exercise caused severe myocardial ischemic-hypoxic injury, which led to an increase in cTnI levels, changes of ischemia–hypoxia, and cells ultrastructure. Compared with the EE group, LEP significantly suppressed exhaustive exercise-induced myocardial injury. However, wortmannin attenuated LEP-induced myocardial protection by inhibiting autophagy. Compared with the C group, AMPK was increased in the LEP, EE, and LEP+EE groups, but phosphorylation of AMPK at Thr172 was not significantly changed. Exercise did not have any effect on mTOR expression. Compared with the C group, ULK1 was increased and the ULK1ser757/ULK1 ratio was decreased in the LEP and LEP+EE groups. ULK1 was not significantly affected in the EE group, however, phosphorylation of ULK1 at Ser757 was remarkably decreased. To sum up, our results suggested that LEP promoted autophagy through the activation of AMPK-mTOR-ULK1 pathway, and that activated autophagy was partially involved in myocardial protection against EE-induced myocardial ischemic-hypoxic injury.

Atg7 Involves In Cardioprotection Induced By Exercise Preconditioning Against Exhaustive Exercise-induced Myocardial Injury

Atg7 Involves In Cardioprotection Induced By Exercise Preconditioning Against Exhaustive Exercise-induced Myocardial Injury

Protective effect of supplementation with Lycium ruthenicum Murray extract from exhaustive exercise-induced cardiac injury in rats.

To the Editor: Lycium ruthenicum (L. ruthenicum) Murray contains abundant anthocyanins. The purpose of the present research was to investigate the protective effect of L. ruthenicum extract supplementation on the damage from exhaustive exercise in rats which were treated for seven days before the exhaustive exercise. Exhaustive exercise induced an increase of Serum nitrate (NO) and reactive oxygen species (ROS) levels, but supplementation of L. ruthenicum extract reduced them significantly (P < 0.05). Interleukin (IL)-1 and IL-6 were also significantly reduced by L. ruthenicum as compared to the control (P < 0.05). Supplementation with L. ruthenicum extract also decreased the creatine kinase isoenzyme MB (CK-MB) generation significantly and ameliorated the myocardial histopathology. L. ruthenicum belongs to the genus Lycium of the family Solanaceae and is a salinized desert plant distributed mainly in Qinghai and Xinjiang Provinces of China. Recently, studies have shown that L. ruthenicum exhibits a wide range of pharmacologic properties, such as anti-oxidation, anti-fatigue, and hypoglycemic activity.[1,2] Anthocyanins and their aglycones from L. ruthenicum have strong antioxidant activity.[3] Anthocyans are flavonols, which occur ubiquitously in the plant kingdom and confer bright red or blue coloration on berries and other fruits and vegetables. Anthocyanin concentration in the L. ruthenicum extract was determined by using the Nakata method[4] and the concentration in the L. ruthenicum extract was 24.1 ± 7.7 mg/g. However, we know anthocyanin has antioxidant properties and ROS induced by extreme temperatures can be protected by anthocyanins in several plants. Anthocyanin has an antioxidant role in plants against ROS and extreme temperatures. Exercise-induced oxidative stress has been reported and antioxidant supplementation can prevent muscle damage, protective effects on the endocrine-metabolic and immune profile.[5] Therefore, L. ruthenicum extract should have a protective effect against oxidative stress and we investigated that the possible protective effect of L. ruthenicum extract and anthocyanin supplementation on the oxidative stress generated by exhaustive exercise in SD rats. In this study, 30 Sprague-Dawley (SD) rats, males and aged 6 weeks, were randomly assigned to the control, anthocyanin (5 mg/rat as the positive control), and other three groups were given L. ruthenicum extract in distilled water orally (as vehicle, 10 and 30 mg/rat), for 7 days before the exhaustive exercise stress. Rats of the exhaustive exercise group were subjected to graded treadmill running started at 10% grade, 15 m/min for 10 min followed by gradual increases of treadmill speed and time as 25 m/min for 20 min, 28 m/min for 20 min, 31 m/min for 20 min, 34 m/min for 20 min, 37 m/min for 20 min until exhaustion. The heart was dissected and washed with saline for fixation with formalin. Exhaustive exercise causes oxidative stress and is defined as the inability of rats to run on the treadmill despite a mild electrical shocking.[6] Add some information on dietary antioxidants for exercise-induced oxidative stress.[7] Regular exercise is recommended for a healthy life, but exhaustive exercise generates the excessive oxidative stress that may exceed the beneficial effect from the regular exercise.[8] In the present study, an increasing CK-MB activity from the cardiac muscle consisted of myocardial damage was seen in tissue vacuoles and cell death from heart tissue. Exhaustive exercise also induced an increase of serum NO, ROS, IL-1, IL-6, and CK-MB levels, but supplementation of L. ruthenicum extract reduced them significantly. Supplementation with L. ruthenicum extract also significantly ameliorated the myocardial histopathology. Under the microscope, the photographs showed the heart section with a 400× magnification. The severity of damage in the exhaustive exercise group was exhibited by vacuoles and dead cells. However, changes in histopathology were significantly reduced by the treatment with anthocyanin and L. ruthenicum extract [Figure 1].Figure 1: Protective effect of Lycium ruthenicum extract on the exhaustive exercise-induced myocardial injury. Histopathology (hematoxylin and eosin staining) of myocardial slices from rats from (A) no treatment control group; (B) the exhaustion group; (C) the Anthocyanin group, exhaustive exercise treatment supplemented with 5 mg Anthocyanin/rat; and (D) the L. ruthenicum extract group, exhaustive exercise treatment supplemented with 30 mg L. ruthenicum/rat. Photographs show the myocardial section with 400× magnification. Tissue vacuoles (hollow triangle arrow heads ▿) and cell death (nuclei stained, black arrow heads ◂) were more severe in exhaustion than those in control or L. ruthenicum groups.In conclusion, 1-week oral supplementation of L. ruthenicum extracts present positive effects on the oxidative stress generated by exhaustive exercise in SD rats, possibly via promotion of antioxidant capacity. The mechanism of protection of L. ruthenicum extract supplementation was not investigated in this study and waits for further study in the future. Acknowledgements The authors are grateful for text proofreading support from Prof. Kee-Ching Jen. Funding None. Conflicts of interest None.

Trimetazidine Attenuates Exhaustive Exercise-Induced Myocardial Injury in Rats via Regulation of the Nrf2/NF-κB Signaling Pathway.

Exhausted exercise has been reported to cause the damage of myocardial structure and function in terms of cardiomyocyte apoptosis, oxidative stress, and energy metabolism disturbance. Trimetazidine (TMZ), as an anti-ischemic agent, has been approved to be effective in promoting myocardial energy metabolism, anti-inflammatory, and anti-oxidation. However, few studies examined the effects of TMZ on myocardial injury induced by exhausted exercise. To investigate whether TMZ could ameliorate the exhaustive exercise-induced myocardial injury and explore the underlying mechanisms, here the rat model of exhaustive exercise was induced by prolonged swimming exercise and TMZ was administrated to rats before exhaustive exercise. According to the results, we demonstrated that exhaustive exercise led to cardiomyocyte damage in rats as evidenced by elevations in cTnI and NT-proBNP levels, and decrease in CX43 expression, which was attenuated by TMZ treatment. Moreover, the administration of TMZ was found to restrain exhaustive exercise-induced oxidative stress damage by increasing GSH level, SOD and GSH-Px activities, and decreasing MDA level. Additionally, TMZ ameliorated myocardial injury by inhibiting apoptosis via reducing Bax/Bcl-2 ratio and down-regulating cleaved caspase-3, cleaved PARP, and cytochrome c levels in the myocardium of rats. Furthermore, we found that TMZ suppressed oxidative stress and cardiomyocyte apoptosis via activation of Nrf2/HO-1 and inactivation of NF-κB signaling pathways. Therefore, our study suggested that TMZ provided cardioprotection in rats after exhaustive exercise, indicating TMZ might served as a potential therapeutic drug for exhaustive exercise-induced myocardial injury.

Role of Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway in cardioprotection of exercise preconditioning.

To investigate the role of Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway in the cardioprotective mechanisms of exercise preconditioning (EP). Eighty male Sprague-Dawley (SD) rats were randomized into the Group control, Group EE, Group EP+EE, Group EP+EE+AG, and Group EE+AG. By using 3 days of intermittent treadmill exercise, this study established the EP animal model. Rats were subjected to run to exhaustion on the treadmill at 30 m/min with 0% grade as an exhaustive exercise (EE) protocol. The myocardial injury induced by exhaustive exercise was produced 24 h after EP. JAK2 inhibitor (AG490, 3 mg/kg) was injected before EP. Serum cardiac troponin I (cTnI) levels and hematoxylin basic fuchsine picric acid (HBFP) staining were used to observe the degree of myocardial ischemia. TUNEL, Bcl2, and cleaved caspase-3 levels were used to evaluate the change of myocardial apoptosis. Moreover, the phosphorylations of JAK2 and STAT3 were analyzed as possible mechanisms that might explain the EP-induced cardioprotection. EP significantly attenuated the exhaustive exercise-induced myocardial ischemia injury, associated with lower serum cTnI levels, decreased myocardial infarct area, reduced myocardial apoptosis, increased Bcl2 level, decreased cleaved caspase-3 level, and the increased phosphorylations of JAK2 and STAT3. Treatment with AG490 abolished the cardioprotective effects and the enhanced phosphorylations of JAK2 and STAT3 induced by EP. EP plays its cardioprotective role via activating the JAK2/STAT3 signaling pathway, reducing the apoptosis of myocardial cells and alleviating myocardial ischemia injury.

MRNA and protein expression of sarcKATP channel subunit Kir6.2 after exercise-induced myocardial injury in rats.

To investigate the expression of kir6.2 subunit of the sarcKATP channel in exercise-induced myocardial injury and to elucidate the underlying mechanism of myocardial protection by sarcKATP channels. Healthy male Sprague Dawley(SD) rats were divided into the Control (C) and the Exhaustive Exercise (EE) group. The one-time exhaustive exercise-induced myocardial injury model was established on a treadmill at a speed of 35 m/min. Alterations in myocardial ischemia and hypoxia were examined by hematoxylin-basic fuchsin-picric acid (HBFP) staining and the concentration of cardiac Troponin I (cTnl), a sensitive and specific marker for myocardial injury, was detected using immunochemiluminescence analysis. The mRNA expression level, localization, and protein expression of sarcKATP channel subunit kir6.2 were determined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), immunofluorescence, and Western blot analysis, respectively. When compared to Group C, rats in Group EE demonstrated significantly increased areas of myocardial ischemia and hypoxia. Moreover, increased serum levels of cTnI were detected. Increased kir6.2 expression was found on the surface of cardiomyocytes and kir6.2 protein expression was also significantly increased. Exercise-induced myocardial injury did not result in noticeable alterations in kir6.2 mRNA expression. However, kir6.2 protein expression was significantly increased and resulted in increased numbers of sarcKATP channel openings in the myocardium, thereby further inhibiting exercise-induced myocardial injury.

The protective effects of Haematococcus pluvialis on the exercise-induced myocardial injury in rat

To study the protective effects of Haematococcus pluvialis (H. pluvialis) on myocardial injury of rats induced by endurance and intensive exercise. The model was based on intensive endurance training. Sixty-five male aged 42 days Wistar rats were randomly divided into 5 groups:control group (C group), general training group (M group), low dose H. pluvialis + training group (HM I group), middle dose H. Pluvialis + training group (HM Ⅱ group), high dose H. pluvialis + training group (HM Ⅲ group). Each group included 12 rats, and the rats were assigned to go on a 42-day swimming training regime. Professional gavage were taken daily. The rats in HM I, HM Ⅱ and HM Ⅲ group were treated with H. pluvialis at the doses of 0.067,0.133 and 0.4 g/kg by ig at 5 ml/kg and the normal saline were given to other groups. After a 42-day swimming training regime, myocardial injury markers such as serum alanine aminotransferase (ALT), myocardial superoxide dismutase(SOD) and malondialdehyde (MDA) were detected, the biochemical indexes such as serum and myocardial endothelin (ET) and calcitonin gene related peptide (CGRP)were detected. Serum ALT, lactate dehydrogenase(LDH), creatine kinase(CK), a-hydroxybutyrate dehydrogenase(a-HBDH), ET, myocardial MDA and ET in M group were significantly higher than those in C group (P<0.05 or P<0.01). The myocardial SOD activity and the myocardial and serum CGRP in M group were significantly lower than those in C group(P<0.05 or P<0.01). The contents of serum ALT, LDH and CK in HM groups were lower than those in the M group but there was no significant difference between the two groups. Compared with M group, H. pluvialis could decrease the levels of serum a-HBDH, ET and myocardial ET in a dose-dependent manner (P<0.05 or P<0.01). The above mentioned three parameters in HM Ⅲ group were lower than those in HM I group (P<0.05). H. pluvialis could decrease the levels of myocardial MDA and increase the levels of myocardial SOD activity and serum or myocardial CGRP in a dose-dependent manner (P<0.05 or P<0.01). The different doses of H.pluvialis can effectively reduce the free radicals caused by endurance and intensive training and enhance the immune function. Meanwhile H.pluvialis is able to guarantee the relative balance in ET an CGRP`s concentration. Therefore, the myocardial lipid peroxidation and myocardial injury are encumbered. Additionaly, high dose of H. pluvialis is proven to be the most effective.