Ischemia-reperfusion Injury In Diabetic Rats Research Articles

Molecular Pathways Involved in the Amelioration of Myocardial Injury in Diabetic Rats by Kaempferol

There is growing evidence that chronic hyperglycemia leads to the formation of advanced glycation end products (AGEs) which exerts its effect via interaction with the receptor for advanced glycation end products (RAGE). AGE-RAGE activation results in oxidative stress and inflammation. It is well known that this mechanism is involved in the pathogenesis of cardiovascular disease in diabetes. Kaempferol, a dietary flavonoid, is known to possess antioxidant, anti-apoptotic, and anti-inflammatory activities. However, little is known about the effect of kaempferol on myocardial ischemia-reperfusion (IR) injury in diabetic rats. Diabetes was induced in male albino Wistar rats using streptozotocin (70 mg/kg; i.p.), and rats with glucose level >250 mg/dL were considered as diabetic. Diabetic rats were treated with vehicle (2 mL/kg; i.p.) and kaempferol (20 mg/kg; i.p.) daily for a period of 28 days and on the 28th day, ischemia was produced by one-stage ligation of the left anterior descending coronary artery for 45 min followed by reperfusion for 60 min. After completion of surgery, rats were sacrificed and the heart tissue was processed for biochemical, morphological, and molecular studies. Kaempferol pretreatment significantly reduced hyperglycemia, maintained hemodynamic function, suppressed AGE-RAGE axis activation, normalized oxidative stress, and preserved morphological alterations. In addition, there was decreased level of inflammatory markers (tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and NF-κB), inhibition of active c-Jun N-terminal kinase (JNK) and p38 proteins, and activation of Extracellular signal regulated kinase 1/2 (ERK1/2) a prosurvival kinase. Furthermore, it also attenuated apoptosis by reducing the expression of pro-apoptotic proteins (Bax and Caspase-3), Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cells, and increasing the level of anti-apoptotic protein (Bcl-2). In conclusion, kaempferol attenuated myocardial ischemia-reperfusion injury in diabetic rats by reducing AGE-RAGE/ mitogen activated protein kinase (MAPK) induced oxidative stress and inflammation.

Effects of p38 mitogen-activated protein kinase on lung ischemia-reperfusion injury in diabetic rats

BackgroundLung ischemia-reperfusion injury (LIRI) is a pathologic process that is observed in several clinical conditions, and p38 mitogen-activated protein kinase (MAPK) is involved. Diabetes mellitus (DM) results in an increased incidence of ischemia-induced organ damage. The aims of this study were to examine the effects of DM on LIRI in a rat model of DM and to explore the possible mechanisms in relation to the p38 MAPK pathway. MethodsForty rats were randomly divided into the following five groups (n = 8 each): a control + sham group, a control + IR group (CIR), a DM + sham group, a DM + IR group (DIR), and a DM + IR + SB203580 group. The control and streptozotocin-induced diabetic rats underwent a sham operation or left hilum occlusion for 90 min followed by reperfusion for 4 h. SB203580 was used to inhibit the p38 MAPK pathway. The pulmonary oxygenation index, inflammatory cytokines in the serum, lung edema, histopathology, oxidant stress, apoptosis, and phosphorylated/total-p38 MAPK protein levels were measured. ResultsThe DIR group displayed greater concentrations of tumor necrosis factor-α, interleukin-6, and intercellular adhesion molecule-1 and increases in the wet weight-to-dry weight ratio, lung injury scores, malondialdehyde levels, and cellular apoptosis, and these effects were accompanied by lower pulmonary oxygenation compared with the CIR group (P < 0.05). In the DIR group, the expression levels of p38 MAPK protein were significantly upregulated compared with those of the CIR group. Additionally, all of these alterations were attenuated in the DM + IR + SB203580 group compared with the DIR group. ConclusionsDiabetes exacerbates LIRI by activating the p38 MAPK pathway.

Protective effect of mangiferin on myocardial ischemia-reperfusion injury in streptozotocin-induced diabetic rats: role of AGE-RAGE/MAPK pathways

Hyperglycemia induced advanced glycation end products-receptor for advanced glycation end products (AGE-RAGE) activation is thought to involve in the development of cardiovascular disease in diabetics. Activation of AGE-RAGE axis results in the oxidative stress and inflammation. Mangiferin is found in the bark of mango tree and is known to treat diseases owing to its various biological activities. Thus, this study was designed to evaluate the effect of mangiferin in ischemia-reperfusion (IR) induced myocardial injury in diabetic rats. A single injection of STZ (70 mg/kg; i.p.) was injected to male albino Wistar rats to induce diabetes. After confirmation of diabetes, rats were administered vehicle (2 ml/kg; i.p.) and mangiferin (40 mg/kg; i.p.) for 28 days. On 28th day, left anterior descending coronary artery was ligated for 45 min and then reperfused for 60 min. Mangiferin treatment significantly improved cardiac function, restored antioxidant status, reduced inflammation, apoptosis and maintained myocardial architecture. Furthermore, mangiferin significantly inhibited the activation of AGE-RAGE axis, c-Jun N-terminal kinase (JNK) and p38 and increased the expression of extracellular regulated kinase 1/2 (ERK1/2) in the myocardium. Thus, mangiferin attenuated IR injury in diabetic rats by modulation of AGE-RAGE/MAPK pathways which further prevented oxidative stress, inflammation and apoptosis in the myocardium.

Inhibition of the Let-7 Family MicroRNAs Induces Cardioprotection Against Ischemia-Reperfusion Injury in Diabetic Rats

The expression of the let-7 family microRNAs in the myocardium of streptozotocin-induced diabetic rats was measured, and the cardioprotection of inhibition of let-7 microRNAs against ischemia-reperfusion injury was investigated. The diabetic rats and nondiabetic rats were subjected to 30 minutes of coronary artery occlusion followed by 120 minutes of reperfusion. The infarct size was determined by triphenyltetrazolium chloride staining. The expression of let-7 was measured by quantitative real-time polymerase chain reaction, and expressions of insulin receptor (InsR), insulin-like growth factor-1 receptor (IGF-1R), glucose transporter type 4 (GLUT4), and the phosphorylation states of Akt and the mammalian target of rapamycin (mTOR) were analyzed using Western blot. Inhibition of let-7 was performed by local transfection of lentivirus gene transfer vectors containing let-7 antimiR. Compared with nondiabetic rats, the expression of let-7 was enhanced in the myocardium of diabetic rats (p= 0.029), whereas expressions of InsR, IGF-1R, and GLUT4 were decreased after ischemia-reperfusion (p < 0.01). Local transfection of the let-7 antimiR markedly inhibited the expression of let-7 (p= 0.038) and improved expressions of InsR, IGF-1R, and GLUT4 in the myocardium of diabetic rats (p < 0.01). The infarct size of diabetic rats was much higher than that of nondiabetic rats (p < 0.0001). Transfection of the let-7 antimiR significantly reduced the infarct size of diabetic rats (p < 0.0001), and such an antiinfarct effect was abolished completely by pretreatment of Akt inhibitor LY294002 or mTOR inhibitor rapamycin. Inhibition of the let-7 family microRNAs improves glucose uptake and insulin resistance in the diabetic myocardium and induces cardioprotection against ischemia-reperfusion injury through Akt and mTOR pathways.

Effects of salvianolate lyophilized injection on neural functional recovery and the expression of microtubule associated protein-2 after focal cerebral ischemia-reperfusion injury in diabetic rats

Objective To investigate the effects of salvianolate lyophilized injection(SLI) on neural functional recovery and the expression of microtubule associated protein-2(MAP2) after focal cerebral ischemia-reperfusion injury in the diabetic rats. Methods Diabetes model was made by intraperitoneal injection of streptozotocin (STZ) and cerebral ischemia-reperfusion model was developed by Longa suture occluded method in the middle cerebral artery of diabetic rats. The rats were randomly divided into five groups: sham operation group, model group, SLI (21.0 mg.kg-1, 10.5 mg.kg-1) treatment groups, and edaravone (6 mg.kg-1) treatment group.3 hours after ischemia, rats were respectively given normal saline or drugs followed by the injection once a day for 14 days and the neurological impairment was assessed. 2 h after the last injection, the rats were decapitated and the brains were collected. The expression of MAP2 protein and mRNA in the bilateral hippocampal ischemia and infarcted area was detected with immunohistochemistry and RT-PCR. Results Severe neurological dysfunction was found in diabetic rats that had been subjected to cerebral ischemic injury(1.850±0.457). A significant improvement on neurological function was found in the SLI treatment groups(1.581±0.314, 1.345±0.425) compared with model group(P<0.01, P<0.05=. Moreover, the expression of MAP2 in ischemia bilateral hippocampal CA1 and penumbra was represented by the average optical density value respectively (0.743±0.250, 0.561±0.224 ). In the hippocampal CA1 region, the number of MAP2-positive cells(0.781±0.420, 0.851±0.136) in the treatment group showed significant increase than those in model group (P<0.01, P<0.05=. In the ischemic penumbra region, the number of MAP2-positive cells (0.753±0.235, 1.203±0.326 ) in the treatment group showed significant increase than those in model group (P<0.01, P<0.05=. Conclusion The SLI can promote the post-injury neurocognitive function in diabetic rats. The increase of MAP2 expression may be involved in the mechanisms. Key words: Diabetes; Cerebral ischemia-reperfusion injury; Salvianolate lyophilized injection; Microtubule associated protein-2

Consequences of exercising on ischemia-reperfusion injury in type 2 diabetic Goto-Kakizaki rat hearts: role of the HO/NOS system.

BackgroundIt is well established that physical exercise continues to be one of the most valuable forms of non-pharmacological therapy against diabetes mellitus; however, the precise mechanism remains unknown. The aim of this study was to investigate the cardioprotective effect of voluntary exercise in the Goto-Kakizaki type 2 diabetic rat heart against ischemia–reperfusion injury and to clarify its biochemical background, focusing on the nitric oxide synthase/heme oxygenase system.MethodsOne group of male Goto-Kakizaki rats were allowed voluntary exercise, whereas others were kept sedentary for 6 weeks. At the end of the 6th week the hearts were isolated from both groups and subjected to 45-min coronary occlusion followed by 120-min reperfusion. The infarct size was evaluated by means of triphenyltetrazolium chloride staining. The cardiac and aortic nitric oxide synthase/heme oxygenase activities, plasma leptin and glucose concentrations were also assessed.ResultsThe sedentary state prior to the ischemia–reperfusion injury was associated with a significantly higher infarct size (24.56 ± 2.21 vs. 16.66 ± 1.87 %) as compared with that in the voluntary wheel-running group. Exercise altered the constitutive nitric oxide synthase activity; an enhancement was evident in the cardiac (42.5 ± 2.72 vs. 75.6 ± 13.34 pmol/min/mg protein) and aortic tissues (382.5 ± 66.57 vs. 576.9 ± 63.16 pmol/min/mg protein). Exercise lead to a higher heme oxygenase activity (0.68 ± 0.08 vs. 0.92 ± 0.04 nmol bilirubin/h/mg protein) in the diabetic rat hearts. Exercise was associated with lower plasma leptin (192.23 ± 7.22 vs. 169.65 ± 4.6 ng/L) and blood glucose (19.61 ± 0.76 vs. 14.58 ± 0.88 mmol/L) levels.ConclusionsThese results indicate the beneficial role of exercise against myocardial ischemia–reperfusion injury in diabetic rats. These observations in experimental diabetes suggest that the cytoprotective mechanism of exercise involves modulation of the nitric oxide synthase/heme oxygenase system and metabolic parameters that may be responsible for cardioprotection.Electronic supplementary materialThe online version of this article (doi:10.1186/s13098-015-0080-x) contains supplementary material, which is available to authorized users.

Changes in expression of mitochondrial fission protein dynamin-related protein-1 during myocardial ischemia-reperfusion injury in diabetic rats

Objective To evaluate the changes in the expression of mitochondrial fission protein dynamin-related protein-1 (Drp1) during myocardial ischemia-reperfusion (I/R) injury in diabetic rats. Methods Sixty healthy adult male Sprague-Dawley rats, weighing 220-250 g, were randomly divided into 4 groups (n=15 each) using a random number table: sham operation group (group S), myocardial I/R group (group I/R), diabetes mellitus (DM) + sham operation group (group DS), and DM + myocardial I/R group (group DI/R). DM was induced by high-fat and high-sucrose diet and intraperitoneal streptozotocin in DS and DI/R groups.Myocardial I/R was produced by occlusion of the anterior descending branch of left coronary artery for 30 min followed by 120 min reperfusion in I/R and DI/R groups.At 120 min of reperfusion, the rats were sacrificed, and myocardial specimens were obtained for measurement of the myocardial infarct size.The myocardial specimens were cut into sections which were stained with haematoxylin and eosin to examine the pathological changes under light microscope.The ultrastructure of mitochondria in cardiomyocytes was observed by electron microscopy.Apoptosis in cardiomyocytes was determined by TUNEL.Apoptosis index (AI) was calculated.The superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured by the methods of xanthine oxidase and thiobarbituric acid, respectively.The expression of myocardial Drp1 protein and mRNA was determined by immunohistochemistry and real-time reverse transcriptase polymerase chain reaction, respectively. Results Compared with group S, the MDA content was significantly increased, the SOD activity was decreased, the expression of Drp1 protein and mRNA was up-regulated, and AI was increased in I/R, DS, and DI/R groups (P<0.05). Compared with group I/R, the MDA content was significantly increased, the SOD activity was decreased, the expression of Drp1 protein and mRNA was up-regulated, AI was increased, and the myocardial infarct size was enlarged in group DI/R (P<0.05). Compared with group DS, the MDA content was significantly increased, the SOD activity was decreased, the expression of Drp1 protein and mRNA was up-regulated, AI was increased, and the myocardial infarct size was enlarged in group DI/R (P<0.05). The pathological changes was aggravated in group DI/R compared with group I/R. Conclusion Myocardial I/R injury is aggravated in diabetic rats, and the mechanism may be associated with up-regulated expression of myocardial Drp1. Key words: Dynamins; Mitochondria; Myocardial reperfusion injury; Diabetes mellitus

Vasonatrin peptide attenuates myocardial ischemia-reperfusion injury in diabetic rats and underlying mechanisms.

Diabetes mellitus increases morbidity/mortality of ischemic heart disease. Although atrial natriuretic peptide and C-type natriuretic peptide reduce the myocardial ischemia-reperfusion damage in nondiabetic rats, whether vasonatrin peptide (VNP), the artificial synthetic chimera of atrial natriuretic peptide and C-type natriuretic peptide, confers cardioprotective effects against ischemia-reperfusion injury, especially in diabetic patients, is still unclear. This study was designed to investigate the effects of VNP on ischemia-reperfusion injury in diabetic rats and to further elucidate its mechanisms. The high-fat diet-fed streptozotocin-induced diabetic Sprague-Dawley rats were subjected to ischemia-reperfusion operation. VNP treatment (100 μg/kg iv, 10 min before reperfusion) significantly improved the instantaneous first derivation of left ventricle pressure (±LV dP/dtmax) and LV systolic pressure and reduced LV end-diastolic pressure, apoptosis index, caspase-3 activity, plasma creatine kinase (CK), and lactate dehydrogenase (LDH) activities. Moreover, VNP inhibited endoplasmic reticulum (ER) stress by suppressing glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). These effects were mimicked by 8-bromine-cyclic guanosinemonophosphate (8-Br-cGMP), a cGMP analog, whereas they were inhibited by KT-5823, the selective inhibitor of PKG. In addition, pretreatment with tauroursodeoxycholic acid (TUDCA), a specific inhibitor of ER stress, could not further promote the VNP's cardioprotective effect in diabetic rats. In vitro H9c2 cardiomyocytes were subjected to hypoxia/reoxygenation and incubated with or without VNP (10(-8) mol/l). Gene knockdown of PKG1α with siRNA blunted VNP inhibition of ER stress and apoptosis, while overexpression of PKG1α resulted in significant decreased ER stress and apoptosis. VNP protects the diabetic heart against ischemia-reperfusion injury by inhibiting ER stress via the cGMP-PKG signaling pathway. These results suggest that VNP may have potential therapeutic value for the diabetic patients with ischemic heart disease.

0213: Gevokizumab, an IL1-beta modulating antibody exerts promising cardioprotective effects against ischemia-reperfusion injury in diabetic rats

Enhanced myocardial interleukin-1 beta (IL1-β) production is involved in ischemia/reperfusion (I/R) induced left ventricular (LV) dysfunction. We tested neutralization of IL-1β as a potential therapeutic target for the treatment of I/R induced LV dysfunction. We assessed in diabetic (Goto Kakizaki, GK) rats the preventive effects of gevokizumab, a potent modulator of IL-1β, administered once a week, started 4 weeks prior to a 20 min of transient ischemia induced by left coronary artery occlusion and continued 90 days after I/R, on LV remodeling/function (echocardiography) 7 and 90 days after I/R. LV hemodynamics (LV catheterization), LV tissue perfusion (MRI) and LV collagen density (image analysis) were assessed 90 days after I/R. I/R induced early LV expansion followed by late LV dilatation, associated with LV dysfunction as well as after 90 days, reduced LV tissue perfusion and LV collagen accumulation. Gevokizumab limited both early LV expansion as well as late LV dilatation, associated with an improved LV function. Ninety days after I/R, gevokizumab improved both LV systolic and LV diastolic functions, illustrated by the increase in LV end-systolic pressure volume relation, and the reductions in LV end-diastolic pressure and LV end-diastolic pressure volume relation. Moreover, long-term gevokizumab moderately increased LV tissue perfusion and significantly reduced LV collagen density. Our results, obtained using a clinically relevant model of I/R, suggest a therapeutic benefit of the IL-1β modulating antibody, gevokizumab, in myocardial I/R injury. LVDD: left ventricular diastolic diameters; LVFS:LV fractional shortening; LVESPVR and LVEDPVR: LV end-diastolic and end-systolic pressure volume relations. *:p<0.05 vs GK; † p<0.05 vs GK I/R

Suv39h1 Protects from Myocardial Ischemia-Reperfusion Injury in Diabetic Rats

Background: Patients with diabetes are at increased risk of ischemic events. Suv39h1 is a histone methyltransferase that catalyzes the methylation of histone 3 lysine 9, which is associated with the suppression of inflammatory genes in diabetes. However, the role of Suv39h1 in myocardial ischemia/reperfusion (I/R) injury under diabetic condition has not been evaluated. Methods: To generate diabetic model, male SD rats were fed with 60% fat diet followed by intraperitoneal injection with 40mg/kg streptozotocin. Adenovirus encoding Suv39h1 gene was used for Suv39h1 overexpression. Each rat received injections of adenovirus at five myocardial sites. Three days after gene transfection, each rat was subjected to left main coronary artery occlusion and reperfusion. After 30 min ischemia and reperfusion for 4 h, the rats were euthanized for real-time PCR, Western blot, immunohistochemical staining, and morphometric analysis. Results: Delivery of Ad-Suv39h1 into the hearts of diabetic rats could markedly increase Suv39h1 expression. Up-regulation of Suv39h1 significantly reduced infarct size and tissue damage after I/R injury, which was associated with protection from apoptosis of cardiac myocytes and reduction of inflammatory response. In addition, compared with injury group, Ad-Suv39h1 led to a decreased activity of mitogen-activated protein kinase family and its down-steam transcriptional factor NF-κB. Conclusion: Overexpression of Suv39h1 results in the de-activation of proinflammatory pathways and reduced apoptosis and myocardial injury. Therefore, Suv39h1 might represent a novel therapeutic strategy to reduce I/R injury under diabetic condition.

Gevokizumab, an IL1-beta modulating antibody exerts promising cardioprotective effects against ischemia-reperfusion injury in diabetic rats

Gevokizumab, an IL1-beta modulating antibody exerts promising cardioprotective effects against ischemia-reperfusion injury in diabetic rats

Intermedin protects against myocardial ischemia-reperfusion injury in diabetic rats

BackgroundDiabetic patients, through incompletely understood mechanisms, endure exacerbated ischemic heart injury compared to non-diabetic patients. Intermedin (IMD) is a novel calcitonin gene-related peptide (CGRP) superfamily member with established cardiovascular protective effects. However, whether IMD protects against diabetic myocardial ischemia/reperfusion (MI/R) injury is unknown.MethodsDiabetes was induced by streptozotocin in Sprague–Dawley rats. Animals were subjected to MI via left circumflex artery ligation for 30 minutes followed by 2 hours R. IMD was administered formally 10 minutes before R. Outcome measures included left ventricular function, oxidative stress, cellular death, infarct size, and inflammation.ResultsIMD levels were significantly decreased in diabetic rats compared to control animals. After MI/R, diabetic rats manifested elevated intermedin levels, both in plasma (64.95 ± 4.84 pmol/L, p < 0.05) and myocardial tissue (9.8 ± 0.60 pmol/L, p < 0.01) compared to pre-MI control values (43.62 ± 3.47 pmol/L and 4.4 ± 0.41). IMD administration to diabetic rats subjected to MI/R decreased oxidative stress product generation, apoptosis, infarct size, and inflammatory cytokine release (p < 0.05 or p < 0.01).ConclusionsBy reducing oxidative stress, inflammation, and apoptosis, IMD may represent a promising novel therapeutic target mitigating diabetic ischemic heart injury.

Effects of NSC23766 on focal cerebral ischemia-reperfusion injury in diabetic rats

Objective To investigate the effects of NSC23766 on focal cerebral ischemia-reperfusion (I/R) injury in diabetic rats.Methods Fifty-one male Sprague-Dawley rats,aged 2-3 months,weighing 250-300 g,in which diabetes mellitus was successfully induced by intraperitoneal streptozotocin 60 mg/kg,were randomly assigned into 3 groups (n=17 each): sham operation group (group S),focal cerebral I/R group (group I/R) and specific Racl inhibitor NSC23766 group (group N).Focal cerebral I/R was induced by middle cerebral arterial occlusion in groups I/R and N.In group N,NSC23766 (50 μg) was injected into the cerebral lateral ventricle at 15 min before ischemia,while the equal volume of normal saline was injected in groups S and I/R.Neurological deficits were scored at 24 h of reperfusion.The rats were then sacrificed and the brains were removed for determination of infarct volume (by TTC staining),apoptosis (by TUNEL) and phosphorylation of p38MAPK (by Western blot)and for microscopic examination (by HE and Nissl staining).Apoptotic index was calculated.Results Compared with group S,the neurological deficit scores aud apoptotic index were significantly increased,the infarct volume was enlarged,and the phosphorylation of p38MAPK was significantly increased in groups I/R and N (P ＜ 0.05).The neurological deficit scores and apoptotic index were significantly lower,and the infarct volume was significantly smaller,and the phosphorylation of p38MAPK was significantly lower in group N than in group I/R (P ＜ 0.05).Conclusion NSC23766 can reduce focal cerebral I/R injury in diabetic rats. Key words: racl GTP-binding protein; Diabetes mellitus; Reperfusion injury; Brain

Role of NO in reduction of myocardial ischemia-reperfusion injury by ginsenoside Rb1 preconditioning in diabetic rats

Objective To evaluate the role of by NO in reduction of myocardial ischemia-reperfusion （IR）injury by ginsenoside Rb1 preconditioning in diabetic rats. Methods Forty healthy adult male SD rats weighing 220-280 g were used in this study. Diabetes mellitus was induced by intraperitoneal streptozotocin 65 mg/kg and confirmed by fasting blood glucose 〉 16.7 mmol/L. The animals were randomly divided into 4 groups （ n = 10each）： sham operation group （group S）, group IR, ginsenoside Rb1 group （group R） and L-NAME ＋ ginsenoside Rb1 group （group LR）. IR was produced by occlusion of the anterior descending branch of left coronary artery （LAD） for 30 min followed by 120 min reperfusion in group IR, R and LR. In group S, LAD was exposed but not occluded. In group LR, L-NAME 10 mg/kg was injected iv 25 min before ischemia. In group R and LR, ginsenoside Rb1 40 mg/kg was injected iv 10 min before ischemia. In group S and IR, eaqual volume of normal saline was injected instead of ginsenoside Rb1. The blood sample was taken from carotid artery at 120 min of reperfusion for determination of serum activities of creatine kinase （CK） and lactate dehydrogenase （LDH）. Then the animals were sacrificed and myocadial tissues were obtained for determination of infarct size, endothelial nitric oxide synthase （eNOS） expression, MDA and NO contents, SOD activity and microscopic examination. Results The serum activities of CK and LDH were significantly increased and the myocardial infarct size was enlarged in group IR, R and LR, and eNOS expression was significantly down-regulated, MDA content was increased, and SOD activity and NO content was significantly decreased in group IR and LR compared with group S （ P 〈 0.05）. The serum activities of CK and LDH, and MDA content were significantly decreased, the myocardial infarct size was reduced, the expression of eNOS was up-regulated and the activity of SOD was increased in group R compared with group IR and LR （ P 〈 0.05）. There was no significant difference in the indices mentioned above between group IR and LR （ P〉 0.05）. Conclusion Ginsenoside Rb1 preconditioning can attenuate myocardial IR injury in diabetic rats via activation of eNOS, increase in NO production, and inhibition of the lipid peroxidation reaction. Key words: Nitric oxide; Ginsenosides; Ischemic preconditioning; Diabetes mellitus; Myocardial reperfusion injury

Effects of postconditioning with leg ischemia on focal cerebral ischemia-reperfusion injury in diabetic rats

Objective To evaluate the effects of leg ischemic postconditioning on focal cerebral ischemia-reperfusion (I/R) injury in diabetic rats. Methods Forty male diabetic SD rats weighing 270-320 g were randomly assigned to one of 4 groups (n=10 each):group Ⅰcontrol (C);group Ⅱ sham operation (S);group Ⅲ fecal cerebral ischemia-repertusion (I/R) and group Ⅳ leg ischemic postconditioning (IPC). Diabetes mellitus was induced by intraperitoneal streptozotocin. Local cerebral I/R was produced by middle cerebral artery occlusion (MCAO) for 1.5 h followed by 6 h reperfusion. A nylon thread with rounded tip was inserted into internal carotid artery and threaded cranially until resistance was felt. Leg isebemia was induced by placing tourniquet on beth legs at 30 min before repeffusion. The animals underwent 3 episodes of 5 min leg ischemia at 5 min intervals. Neuro-functional deficit was assessed and recorded at the end of 6h reperfusion using neurologic deficit scores (NDS) (0=no deficit, 4=unable to crawl and semiconscious). The animals were then decapitated and their brains were removed for determination of volume of cerebral infaret (by TIC staining) and ratio' of neuronal apoptosis (by TUNEL). Results NDS and cerebral infarct volume were significantly increased at the end of 6 h reperfusion in group I/R and IPC as compared with group C and S. IPC significantly decreased cerebral infarct volume and ratio of neuronal apoptosis induced by MCAO. There was no significant difference in NDA between group I/R and IPC. Conclusion Leg iscbemic postconditioning can protect the brain against focal cerebral I/R injury in diabetic rats. Key words: Lower extremity; Reperfusion injury; Brain; Diabetes mellitus; lscbemic postconditioning