Single and 7-day handgrip and squat exercise prevents endothelial ischemia-reperfusion injury in individuals with cardiovascular disease risk factors

Whole body exercise provides protection against endothelial ischemia-reperfusion (IR) injury. In this crossover study, we examined the effects of 1) single bout of local exercise (handgrip, squats) on endothelial responses to IR, and 2) if 7 days of daily local exercise bolsters these effects in individuals with cardiovascular disease (CVD) risk factors. Fifteen participants (9 women, 58 ± 5 yr, ≥2 CVD risk factors) attended the laboratory for six visits. Subsequent to familiarization (visit 1), during visit 2 (control) brachial artery flow-mediated dilation (FMD) was measured before and after IR (15-min upper-arm ischemia, 15-min reperfusion). One week later, participants were randomized to 4 × 5-min unilateral handgrip (50% maximal voluntary contraction, 25 rpm) or squat exercises (15 rpm), followed by IR plus FMD measurements. Subsequently, home-based exercise was performed (6 days), followed by another visit to the laboratory for the IR protocol plus FMD measurements (18-24 h after the last exercise bout). After a 2-wk washout period, procedures were repeated with the alternative exercise mode. For a single exercise bout, we found a significant IR injury × exercise mode interaction (P < 0.01) but no main effect of injury (P = 0.08) or condition (P = 0.61). A lower post-IR FMD was evident after control (pre-IR: 4.3 ± 2.1% to post-IR: 2.9 ± 1.9%, P < 0.01) but not after handgrip (pre-IR: 3.8 ± 1.6% to post-IR: 3.4 ± 1.5%, P = 0.31) or squats (pre-IR: 3.9 ± 1.8% to post-IR: 4.0 ± 1.9%, P = 0.74). After 7 days of daily exercise, we found no change in FMD post-IR following handgrip (pre-IR: 4.3 ± 1.9% to post-IR: 4.7 ± 3.2%) or squats (pre-IR: 3.7 ± 2.1% to post-IR: 4.7 ± 3.0%, P > 0.05). Single bouts of dynamic, local exercise (handgrip, squats) provide remote protection against endothelial IR-induced injury in individuals with CVD risk factors, with 1-wk daily, home-based exercise preserving these effects for up to 24 h following the last exercise bout.NEW & NOTEWORTHY We show that single bouts of dynamic handgrip and squat exercise provide remote protection against endothelial ischemia-reperfusion (IR)-induced injury in individuals with cardiovascular disease (CVD) risk factors, with 1-wk daily, home-based exercise preserving these effects for up to 24 h following the last exercise bout.

Handgrip exercise in patients scheduled for cardiac surgery to attenuate troponin release: a feasibility study

Cardiac surgery, including surgical aortic valve repair (SAVR) and coronary artery bypass grafting (CABG), are associated with ischemia-reperfusion (I/R) injury. Single bouts of exercise, including handgrip exercise, may protect against I/R injury. This study explored 1) the feasibility of daily handgrip exercise in the week before SAVR and/or CABG and 2) its impact on cardiac I/R injury, measured as postoperative cardiac troponin-T (cTnT) release. Sixty-five patients undergoing elective SAVR and/or CABG were randomized to handgrip exercise + usual care (intervention, n = 33) or usual care alone (control, n = 32). Handgrip exercise consisted of daily 4 × 5-min handgrip exercise (30% maximal voluntary contraction) for 2-7 days before cardiac surgery. Feasibility was assessed using validated questionnaires. Postoperative cTnT release was assessed at 0, 6, 12, 18, and 24 h [primary outcome area under the curve (cTnTAUC)]. Most patients (93%) adhered to handgrip exercise and 77% was satisfied with this intervention. Handgrip exercise was associated with lower cTnTAUC (402,943 ± 225,206 vs. 473,300 ± 232,682 ng · min/L), which is suggestive of a medium effect size (Cohen's d 0.31), and lower cTnTpeak (313 [190-623] vs. 379 [254-699] ng/L) compared with controls. We found that preoperative handgrip exercise is safe and feasible for patients scheduled for SAVR and/or CABG and is associated with a medium effect size to reduce postoperative cardiac I/R injury. This warrants future studies to assess the potential clinical impact of exercise protocols before cardiac surgery.NEW & NOTEWORTHY Daily handgrip exercise in the week before elective cardiac surgery is safe and feasible. Handgrip exercise is associated with a medium effect size for less troponin-T release. Future larger-sized studies are warranted to explore the impact of (handgrip) exercise prior to cardiac surgery on clinical outcomes and direct patient benefits.

Effects of Exercise Preconditioning on Doxorubicin-Induced Liver and Kidney Toxicity in Male and Female Rats

Doxorubicin (DOX) is a highly effective chemotherapy agent prescribed for cancer treatment. However, the clinical use of DOX is limited due to off-target toxicity in healthy tissues. In this regard, hepatic and renal metabolic clearance results in DOX accumulation within these organ systems. Within the liver and kidneys, DOX causes inflammation and oxidative stress, which promotes cytotoxic cellular signaling. While there is currently no standard of care to treat DOX hepatic- and nephrotoxicity, endurance exercise preconditioning may be an effective intervention to prevent elevations in liver alanine transaminase (ALT) and aspartate aminotransferase (AST) and to improve kidney creatinine clearance. To determine whether exercise preconditioning is sufficient to reduce liver and kidney toxicity resulting from acute exposure to DOX chemotherapy treatment, male and female Sprague-Dawley rats remained sedentary or were exercise trained prior to saline or DOX exposure. Our findings demonstrate that DOX treatment elevated AST and AST/ALT in male rats, with no effects of exercise preconditioning to prevent these increases. We also showed increased plasma markers of renin-angiotensin-aldosterone system (RAAS) activation and urine markers of proteinuria and proximal tubule damage, with male rats revealing greater differences compared to females. Exercise preconditioning showed improved urine creatinine clearance and reduced cystatin c in males, while females had reduced plasma angiotensin II (AngII) levels. Our results demonstrate both tissue- and sex-specific responses related to the effects of exercise preconditioning and DOX treatment on markers of liver and kidney toxicity.

Exercise preconditioning attenuates cerebral ischemia-induced neuronal apoptosis, Th17/Treg imbalance, and inflammation in rats by inhibiting the JAK2/STAT3 pathway

BACKGROUND

Exercise preconditioning (EP) is essential for preventing ischemic stroke. Recent studies have shown that EP exerts neuroprotective effects in the cerebral ischemia-reperfusion injury model. Nonetheless, there have been few reports on the relationship between EP and the Th17/Treg balance. Moreover, it is unclear whether the JAK2/STAT3 pathway is responsible for the neuroprotective effect of EP. Therefore, we aimed to explore the impact of EP, other than the anti-inflammatory and antiapoptotic functions, on the Th17/Treg balance via the JAK2/STAT3 pathway in a middle cerebral artery occlusion (MCAO)-induced model.

RESULTS

Fifty rats were randomly allocated into five groups, including the sham group (n = 10), EP+sham group (n = 10), MCAO group (n = 10), EP+MCAO group (n = 10), and EP+MCAO+JAK2/STAT3 pathway agonist (coumermycin A1, CA1) group (n = 10). The results indicated that EP alleviated neurological deficits, reduced infarct volume, and ameliorated neuronal apoptosis induced by MCAO. Additionally, the MCAO-induced Th17/Treg imbalance could be rectified by EP. The decreased levels of IL-10 and Foxp3 and increased IL-17 and RORα in the MCAO group were reversed by EP treatment. Regarding inflammation, EP reduced the concentrations of IL-6 and IL-17 and elevated those of IL-10 and TGF-β. The neuroprotective effects of EP were accompanied by decreased phosphorylation of JAK2 and STAT3. Furthermore, CA1 pretreatment diminished all the beneficial effects of EP partially.

CONCLUSION

Our findings suggest that EP contributes to attenuating neuronal apoptosis, Th17/Treg imbalance, and inflammation induced by MCAO via inhibiting the JAK2/STAT3 pathway, indicating its therapeutic potential in ischemic stroke.

Impact of handgrip exercise and ischemic preconditioning on local and remote protection against endothelial reperfusion injury in young men

Ischemic preconditioning (IPC), cyclical bouts of nonlethal ischemia, provides immediate protection against ischemic injury, which is evident both locally and remotely. Given the similarities in protective effects of exercise with ischemic preconditioning, we examined whether handgrip exercise also offers protection against endothelial ischemia-reperfusion (IR) injury and whether this protection is equally present in the local (exercised) and remote (contralateral, nonexercised) arm. Fifteen healthy males (age, 24 ± 3 yr; body mass index, 25 ± 2 kg/m²) attended the laboratory on three occasions. Bilateral brachial artery flow-mediated dilation (FMD) was examined at rest and after a temporary IR injury in the upper arm. Before the IR injury, in the dominant (local) arm, participants performed (randomized, counterbalanced): 1) 4 × 5 min unilateral handgrip exercise (50% maximal voluntary contraction), 2) 4 × 5 min unilateral IPC (220 mmHg), or 3) 4 × 5 min rest (control). Data were analyzed using repeated-measures general linear models. Allometrically scaled FMD declined after IR in the control condition (4.6 ± 1.3% to 2.2 ± 1.7%, P < 0.001), as well as following handgrip exercise (4.6 ± 1.6% to 3.4 ± 1.9%, P = 0.01), however, was significantly attenuated with IPC (4.5 ± 1.4% to 3.8 ± 3.5%, P = 0.14). There were no differences between the local and remote arm. Our findings reinforce the established protective effects of IPC in young, healthy males and also highlight a novel strategy to protect against IR injury with handgrip exercise, which warrants further study.

Insight Into the Mechanism of Exercise Preconditioning in Ischemic Stroke

Exercise preconditioning has attracted extensive attention to induce endogenous neuroprotection and has become the hotspot in neurotherapy. The training exercise is given multiple times before cerebral ischemia, effectively inducing ischemic tolerance and alleviating secondary brain damage post-stroke. Compared with other preconditioning methods, the main advantages of exercise include easy clinical operation and being readily accepted by patients. However, the specific mechanism behind exercise preconditioning to ameliorate brain injury is complex. It involves multi-pathway and multi-target regulation, including regulation of inflammatory response, oxidative stress, apoptosis inhibition, and neurogenesis promotion. The current review summarizes the recent studies on the mechanism of neuroprotection induced by exercise, providing the theoretical basis of applying exercise therapy to prevent and treat ischemic stroke. In addition, we highlight the various limitations and future challenges of translational medicine from fundamental study to clinical application.

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% VO_2max) 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.

Study on the time-effectiveness of exercise preconditioning on heart protection in exhausted rats

To investigate the persistence time and the effectiveness of exercise preconditioning (EP) on myocardial protection in exhausted rats from myocardial enzymes, electrocardiogram (ECG), cardiac function, and mitochondrial respiratory function after cessation of exercise training. One hundred and twelve healthy male Sprague-Dawley rats were randomly divided into seven groups (n = 16): control group (CON), exhaustive exercise (EE) group, EP group, and EE after EP (EP + EE); furthermore, EP + EE group was randomly divided into 1D, 3D, 9D, and 18D groups (1D, 3D, 9D, and 18D) and performed exhaustive treadmill exercise at a speed of 30 m/min on the 1^st, 3^rd, 9^th, and 18^th days separately after EP exercise stopped. We detected the serum contents of N-terminal pro B type natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) by the enzyme-linked immunosorbent assays method, recorded ECG, detected heart function by pressure volume catheter, measured the respiratory rates of rat myocardial mitochondria state 3 and 4 of complex I, complex II, and IV by high-resolution breathing apparatus. EP could decrease the serum content of NT-proBNP and cTnI, improved the electrical derangement and the left ventricular function in exhausted rats. Moreover, the protective effect was more obvious in the 9^th day after EP stopped, whereas it would disappear when EP stopped for more than 18 days. Compared with EE group, the respiratory rate value of myocardial mitochondrial complex increased in 1D, 3D, and 9D groups. Therefore, the protective effect of EP on the heart of exhausted rats decreased with the prolongation of stopping training time, and the effect was significant within 3 days of discontinuing training, then decreased gradually, and completely disappeared in the 18^th day. EP enhanced the cardiac function in exhausted rats through raising the nicotinamide adenine diphosphate hydride (NADH) electron transport chain and increased the respiration rates of mitochondrial respiratory complex I and IV state 3, thereby improved myocardial mitochondrial respiratory function and energy metabolism.

Preconditioning by aerobic exercise reduces acute ischemic renal injury in rats

Acute kidney injury (AKI) can be defined as the sudden loss of renal function associated with structural changes in the kidneys. Currently, 13.3 million people die of AKI around the world. Normally aerobic exercise is used both as/for the treatment and prevention of high blood pressure, metabolic disease and Diabetes mellitus (DM). Nevertheless, exercise preconditioning must be a crucial resource in the prevention and mitigation of AKI. The aim of this study was to evaluate the effects of the exercise preconditioning on renal IR (ischemic/reperfusion) experimental model. Male Wistars rats were divided into three groups (n = 9): sham (S), ischemic/reperfusion (IR), exercise + ischemic/reperfusion (EX + IR). IR renal injury was induced by clamping the bilateral renal artery for 45 min. The rats were subjected to exercise 5 days a week for 4 weeks with progressive intensity and duration. The group treated with exercise preconditioning, showed additional improvements in various parameters, including serum creatinine, proteinuria, and decrease of the severity of the tubular injury and activated caspase‐3 levels (P < 0.05). The previous aerobic exercise‐induced renoprotection in the IR injury. We anticipate that the practice of physical exercise in healthy individuals can also be useful for the prevention and attenuation of AKI.

The effect of exercise preconditioning on stroke outcome in ovariectomized mice with permanent middle cerebral artery occlusion

Exercise preconditioning has been shown to be effective in improving behavioral and neuropathological indices after cerebral ischemia. We evaluated the effect of exercise preconditioning, 17β-estradiol, and their combination on stroke outcome using an experimental model of stroke in ovariectomized (OVX) mice. OVX mice were randomly assigned to 4 groups as follows: control (stroke), exercise (exercise and stroke), estradiol (17β-estradiol and stroke), and exercise+estradiol (exercise and 17β-estradiol and stroke). Exercise preconditioning was performed on a treadmill 5 days/week, 40 min/day, at a speed of 18 m/min for 4 weeks. 17β-estradiol was gavaged (40 μg/kg per day) for 4 weeks. Stroke was induced by permanent middle cerebral artery occlusion (pMCAO), and neurological deficits were evaluated 1, 2, and 7 days after stroke. Then, the serum concentrations of matrix metalloproteinase-9 (MMP-9) and interleukin-10 (IL-10) and infarct volumes were assessed. Exercise preconditioning and 17β-estradiol induced a better outcome compared with the control ischemic mice, which was manifested by decrease in MMP-9, increase in IL-10, diminished infarct volume, and improved neurological deficits. Concomitant administration of 17β-estradiol and exercise also significantly improved these parameters. Exercise preconditioning or administration of 17β-estradiol alone or in combination before pMCAO induced significant neuroprotection in OVX mice.

[Protective effects of short-term and long-term exercise preconditioning on myocardial injury in rats]

OBJECTIVE

To study the role and mechanism of myocardial apoptosis after short-term and long-term exercise preconditioning.

METHODS

Forty-eight male SD rats were randomly divided into control group (C), exhaust group (E), short-exercise preconditioning (S-EP) and long-term exercise preconditioning group (L-EP). Short-term and long-term exercise preconditioning were conducted for 3 days and 3 weeks of repeated intermittent swimming training program. The changes of myocardial cells were observed under light microscope. The serum levels of ischemia-modified albumin(IMA) and creatine kinase-isoenzyme(CK-MB) were detected by ELISA. Real time fluorescence quantitative PCR and Western blot were used to detect the expressions of tumor necrosis factor-α(TNF-α),Caspase-8, Caspase-3 genes and proteins in myocardial tissue. The apoptosis of cardiomyocytes was observed by TUNEL method.

RESULTS

Compared with group C, group E had serious myocardial injury. The levels of serum IMA, CK-MB and the expressions of TNF-α, Caspase-8 and Caspase-3 in myocardium were increased (P<0.05). Compared with group E, serum CK-MB and TNF-α and Caspase-8 mRNA in S-EP group were significantly lower than those in group E (P<0.05), but there was no significant difference in serum IMA and Caspase-3 mRNA and protein (P>0.05). The levels of serum IMA, CK-MB and TNF-α, Caspase-8 and Caspase-3 mRNA in L-EP group were significantly lower than those in control group (P<0.05). The apoptosis of cardiomyocytes in group E was obvious. Short-term and long-term exercise preconditioning could inhibit apoptosis. Compared with S-EP group, the apoptosis of L-EP group was significantly decreased.

CONCLUSIONS

Short-term and long-term exercise preconditioning can reduce myocardial injury after exhaustive exercise, but short-term exercise preconditioning does not alter the expression of Caspase protease. Long-term exercise preconditioning significantly inhibits Caspase-8, 3 mRNA expression and reduces protein synthesis. The inhibitive effects of long-term exercise preconditioning on myocardial cell apoptosis were stronger than those of short-term exercise preconditioning.

[The role of JAK2/STAT3 signaling pathway in exercise preconditioning against myocardial apoptosis]

OBJECTIVE

To study the effects of Janus kinase 2/signal transducers and activators of transcription 3 (JAK2/STAT3) in exercise preconditioning (EP) against myocardial apoptosis.

METHODS

Eighty healthy male SD rats were randomly divided into control group(C), exercise exhaust(EE) group, EP group, and EP+JAK2 inhibitor AG490(AG) group(n=20). By using 3 days intermittent treadmill exercise, the EP animal model was established, and myocardial injury was induced by exhaustive exercise on treadmill. The changes of myocardial apoptosis were evaluated by TUNEL. The expressions of Caspase-3, p-JAK2 and p-STAT3 in heart were detected by Western blot or immunohistochemistry.

RESULTS

Compared with group C, myocardial apoptosis, and the expressions of Caspase-3, p-JAK2, and p-STAT3 in heart were increased significantly in group EE. Compared with group EE, myocardial apoptosis and the expression of Caspase-3 were decreased significantly, while the expressions of p-JAK2 and p-STAT3 were increased significantly in group EP. Compared with group EP, myocardial apoptosis and the expression of Caspase-3 were increased significantly, while the expressions of p-JAK2 and p-STAT3 were decreased significantly in group EP+AG.

CONCLUSIONS

EP could increase the expressions of p-JAK2 and p-STAT3 and decrease the expression of Caspase-3 in heart, which further mitigate myocardial apoptosis. Hence, JAK2/STAT3 pathway may participate in EP against myocardial apoptosis.

A Pilot Study to Assess Adenosine 5'-triphosphate Metabolism in Red Blood Cells as a Drug Target for Potential Cardiovascular Protection

OBJECTIVE

To study the effect of exercise preconditioning on adenosine 5'triphosphate (ATP) metabolism in red blood cells and cardiovascular protection against injury induced by isoproterenol in vivo.

METHODS

Male Sprague Dawley rats (SDR) were each exercised on a treadmill for 15 minutes at 10 m/min and 10% grade (n = 7) (LowEx), or 14 m/min and 22% grade (n = 8) (VigEx). Two hours after the exercise, each rat received a single dose of isoproterenol (30 mg/kg) by subcutaneous (sc) injection. Two separate groups of SDR were used as control: One received no exercise (n = 10) (NoEx) and the other received no exercise and no isoproterenol (n = 11) (NoIso). Serial blood samples were collected over 5 hours for measurement of ATP and its catabolites by a validated HPLC. Hemodynamic recording was collected continuously for the duration of the experiment. Data were analysed using ANOVA and t-tests and difference considered significant at p < 0.05.

RESULTS

Exercise pre-conditioning (both LowEx and VigEx) reduced mortality after isoproterenol from 50% to < 30% (p > 0.05). It attenuated the rebound in blood pressure significantly (p < 0.05 between NoEx vs VigEx), attenuated the increase of RBC adenosine 5'-monophosphate (AMP) concentrations induced by isoproterenol, and also decreased the breakdown of ATP to AMP in the RBC (p < 0.05 vs NoEx).

CONCLUSION

Exercise pre-conditioning decreased the blood pressure rebound and also breakdown of ATP in RBC after isoproterenol which may be exploited further as a drug target for cardiovascular protection and prevention.

Exercise preconditioning-induced late phase of cardioprotection against exhaustive exercise: possible role of protein kinase C delta

The objective of this study was to investigate the late cardiac effect of exercise preconditioning (EP) on the exhaustive exercise-induced myocardial injury in rats and the role of protein kinase C (PKC) in EP. Rats were subjected to a run on the treadmill for four periods of 10 min each at 30 m/min with intervening periods of rest of 10 min as an EP protocol. The exhaustive exercise was performed 24 h after EP. PKC inhibitor chelerythrine (CHE) was injected before EP. The results showed that EP increased the running ability of rats, and alleviated the exhaustive exercise-induced injury in cardiomyocytes, but pretreatment with PKC inhibitor CHE did not abolish the late phase cardioprotection of EP. A significant increase of PKCδ, both at the protein level and the mRNA level in the left ventricular myocardium of rats, accompanied by its activated form (phosphorylated on Thr507, p-PKCδThr507) translocated to intercalated disks and was found in the late phase of EP. This circumstance was not attenuated by CHE. These results suggested that a high level of PKCδ might be involved in cardioprotection against myocardial damage, but if activated PKCδ at reperfusion took on a key role in cardioprotection was still an outstanding question.

Pre-ischemic treadmill training alleviates brain damage via GLT-1-mediated signal pathway after ischemic stroke in rats

Physical exercise could play a neuroprotective role in both human and animals. However, the involved signal pathways underlying the neuroprotective effect are still not well established. This study was to investigate the possible signal pathways involved in the neuroprotection of pre-ischemic treadmill training after ischemic stroke. Seventy-two SD rats were randomly assigned into three groups (n=24/group): sham surgery group, middle cerebral artery occlusion (MCAO) group and MCAO with exercise group. Following three weeks of treadmill training exercise, ischemic stroke was induced by occluding the middle cerebral artery (MCA) in rat for 2 h, followed by reperfusion. Twenty-four hours after MCAO/reperfusion, 12 rats in each group were evaluated for neurological deficit scores and then sacrificed to measure the infarct volume (n=6) and cerebral edema (n=6). Six rats in each group were sacrificed to measure the expression level of glutamate transporter-1 (GLT-1), protein kinase C-α (PKC-α), Akt, and phosphatidylinositol 3 kinase (PI3K) (n=6). Two hundred and eighty minutes (4.67 h) after occlusion, six rats in each group were decapitated to detect the mRNA expression level of metabotropic glutamate receptor 5 (mGluR5) and N-methyl-D-aspartate receptor subunit type 2B (NR2B) (n=6).The results demonstrated that pre-ischemic treadmill training exercise reduced brain infarct volume, cerebral edema and neurological deficits, also decreased the over expression of PKC-α and increased the expression level of GLT-1, Akt and PI3K after ischemic stroke (p<0.05). The over-expression of mGluR5 and NR2B mRNA was also inhibited by pre-ischemic exercise (p<0.05). In summary, exercise preconditioning ameliorated brain damage after ischemic stroke, which might be involved in two signal pathways: PKC-α-GLT-1-Glutamate and PI3K/Akt-GLT-1-Glutamate.

Exercise reduces infarct volume and facilitates neurobehavioral recovery: results from a systematic review and meta-analysis of exercise in experimental models of focal ischemia

BACKGROUND

Regular exercise reduces the risk of a first-ever stroke and is associated with smaller infarcts. Although evidence has suggested that therapeutic exercise following stroke is beneficial, we do not yet know whether exercise reduces stroke severity and improves functional recovery. The mechanisms underlying any benefit remain unclear.

OBJECTIVE

To conduct a systematic review and meta-analysis of studies testing exercise in animal models of ischemic stroke where outcomes were measured as infarct volume, neurobehavioral score, neurogenesis, or a combination of these. We also sought evidence of publication bias.

METHODS

We searched 3 online databases for publications reporting the use of exercise in focal cerebral ischemia. We used DerSimonian and Laird normalized random-effects meta-analysis and meta-regression to determine the impact of study quality and design on the efficacy of exercise. RESULTS. Overall, exercise reduced infarct volume by 25.2% (95% confidence interval [CI] = 19.0%-31.3%; 65 experiments and 986 animals) and improved neurobehavioral score by 38.2% (95% CI = 29.1%-47.3%; 42 experiments; n = 771). For both outcomes, larger effects were seen when exercise preceded ischemia rather than came after it. For neurobehavioral scores, we found evidence of publication bias. Reported study quality was moderate (median score 5/10). Both model-specific (e.g., type of ischemia) and exercise-specific characteristics influenced reported outcome. CONCLUSION. Exercise, either before or after ischemia, reduced infarct volume and improved neurobehavioral score. However, overall estimates of efficacy were higher in studies at risk of bias, and for neurobehavioral outcomes, there was evidence of a substantial publication bias.

Exercise preconditioning initiates late cardioprotection against isoproterenol-induced myocardial injury in rats independent of protein kinase C

The objective of this study was to investigate the late cardioprotective effect of exercise preconditioning (EP) on isoproterenol (ISO)-induced myocardial injury in rats and the role of protein kinase C (PKC) in EP. Rats were injected with ISO 24 h after running on a treadmill for four periods of 10 min each at 28-30 m/min with intervening periods of rest of 10 min. Nonselective PKC inhibitor chelerythrine (CHE) was injected before EP. The myocardial injury was evaluated quantitatively in terms of the serum cardiac troponin I (cTnI) levels, the myocardial ischemia/hypoxia area, and the integral optical density (IOD) of haematoxylin-basic fuchsin-picric acid (HBFP) staining, and qualitatively in terms of the myocardial ultrastructure. EP markedly attenuated the ISO-induced myocardial ischemia/hypoxia and ultrastructural damage with lower serum cTnI levels. CHE injection before EP did not block the protective effect of EP, displaying a mild myocardial ischemia/hypoxia and well-preserved ultrastructure with even lower serum cTnI levels. The results indicate that EP can exert a late cardioprotection against ISO-induced myocardial injury, and that an injection of the nonselective PKC inhibitor CHE before EP may have a different effect on ISO-induced myocardial injury. Further investigation needs to be conducted to define the role of different PKC isozymes in EP by using isozyme-selective inhibitors.