Glucagon-like peptide-1 protects against cardiac microvascular endothelial cells injured by high glucose

Objective:To investigate the protective effect of glucagon-like peptid-1(GLP-l) against cardiac microvascular endothelial cell(GTFCs) injured by high glucose.Methods:CMECs were isolated and cultured.Superoxide assay kit and dihydroethidine(DHE) staining were used to assess oxidative stress.TENEL staining and caspase 3 expression were used to assess the apoptosis of CMECs.H89 was used to inhibit eAMP/PKA pathway:fasudil was used to inhibit Rho/ROCK pathway.The protein expressions of Rho.ROCK uere examined by Western blol analysis.lesults:High glucose increased the production of ROS.the activity of NADPH.the apoptosis rate and the expression level of Rho/ROCK in CMECs.while GLP- 1 decreased high glucose-induced ROS production.the NADPH activity and the apoptosis rate and the expression level of Rho/ROCK in CMECs,the difference were statistically significant(P0.05).Conclusions:GLP-1 could protect the cardiac microvessels against oxidative stress and apoptosis.The protective effects of GLP-1 are dependent on downstream inhibition of Rho through a cAMP/PKA-dependent manner,resulting in a subsequent decrease in the expression of NADPH oxidase.     

烟酰胺核糖抑制1型糖尿病大鼠心肌线粒体分裂的作用及机制

目的 探讨烟酰胺核糖（nicotinamide riboside, NR）对1型糖尿病（DM）大鼠心肌线粒体融合分裂的作用及其机制。 方法 利用链脲佐菌素（streptozotocin, STZ）诱导1型DM大鼠模型,随机分为4组:正常对照（Con）组,Con+NR组,DM组,DM+NR组。监测大鼠血糖和体质量变化,葡萄糖耐量试验（IPGTT）检测糖代谢情况,采用小动物超声评估大鼠心脏功能变化,TUNEL法检测心肌细胞凋亡,DHE染色检测心肌细胞ROS含量,透射电镜观察线粒体形态,Western blot法检测线粒体分裂、融合相关蛋白表达水平。 结果 与Con组相比,DM组大鼠的血糖、血脂明显升高,体质量减轻,心脏左室射血分数（left ventricular ejection fraction, LVEF）和左心室短轴缩短率（Left ventricular fractional shortening, LVFS）减低,心肌细胞凋亡增加,氧化应激增强,线粒体分裂增多,线粒体融合蛋白Opa1表达下调（P<0.05, P<0.01）;与DM组相比,DM+NR组大鼠心脏LVEF改善,心肌细胞凋亡减少,氧化应激减少,线粒体融合增加,线粒体融合蛋白Opa1和Mfn2表达上调（P<0.05）。 结论 NR可增加DM心肌融合蛋白Opa1与Mfn2的表达,抑制DM心肌线粒体分裂,降低DM心肌凋亡和氧化应激,改善心脏功能。     

Novel mechanism of angiotensin II-induced cardiac injury in hypertensive rats: the critical role of ASK1 and VEGF

This study was undertaken to elucidate a novel mechanism underlying angiotensin II-induced cardiac injury, focusing on the role of oxidative stress and myocardial capillary density. Salt-loaded Dahl salt-sensitive hypertensive rats (DS rats), a useful model for hypertensive cardiac remodeling or heart failure, were orally given irbesartan (an AT1 receptor blocker), tempol (a superoxide dismutase mimetic) or hydralazine (a vasodilator). Irbesartan significantly ameliorated left ventricular ischemia and prevented the development of cardiac hypertrophy and fibrosis in DS rats. The benefits were associated with the attenuation of oxidative stress, normalization of myocardial capillary density and inhibition of capillary endothelial apoptosis. Moreover, DS rats with significant cardiac hypertrophy and fibrosis displayed decreased myocardial vascular endothelial growth factor (VEGF) expression and increased cardiac apoptosis signal-regulating kinase 1 (ASK1) activation. Treatment with irbesartan significantly reversed these phenotypes. Tempol treatment of DS rats mimicked all the above-mentioned effects of irbesartan, indicating the critical role of oxidative stress in cardiac injury. We also investigated the role of VEGF and ASK1 in oxidative stress-induced endothelial apoptosis by using cultured endothelial cells from wild-type and ASK1-deficient mice. Oxidative stress-induced ASK1 activation led to endothelial apoptosis, and VEGF treatment prevented oxidative stress-induced endothelial apoptosis by inhibiting ASK1 activation. We obtained the first evidence that oxidative stress-induced cardiac VEGF repression and ASK1 activation caused the enhancement of endothelial apoptosis and contributed to a decrease in myocardial capillary density. These effects resulted in angiotensin II-induced progression of cardiac injury.     

阿托伐他汀对高同型半胱氨酸血症诱发动脉粥样硬化的干预作用

目的:观察阿托伐他汀对动脉粥样硬化斑块的影响, 并对其作用机制进行初步探讨。方法: 20 g/L L-蛋氨酸灌胃法建立ApoE基因敲除小鼠高同型半胱氨酸血症(hyperhomocysteinemia,HHcy)模型,按实验分组, 给予不同剂量阿托伐他汀治疗1个月后,用高效液相色谱荧光法测定血浆同型半胱氨酸(Hcy)水平,相差显微镜下观察小鼠主动脉根部病理学形态,免疫组织化学法检测主动脉血管平滑肌SM-α-actin的表达,TUNEL法检测小鼠主动脉斑块中的细胞凋亡指数,NBT及光泽精化学发光法检测血管局部活性氧(reactive oxygen species,ROS)水平, 光泽精化学发光法检测主动脉血管NADPH氧化酶(NADPH oxidase,Nox)活性,Western印迹法检测Nox4蛋白表达。结果: ApoE-/-小鼠蛋氨酸喂养3个月后,血浆Hcy水平升高,AS斑块形成。阿托伐他汀治疗1个月后,呈剂量依赖性地降低小鼠血浆Hcy水平,延缓AS病变的进程,减少斑块内凋亡细胞数量,降低了血管壁局部ROS水平,Nox活性及Nox4蛋白表达（均P<0.05）。结论: 阿托伐他汀治疗后,HHcy ApoE-/-小鼠AS病变进程延缓,其作用机制与其下调Nox4来源的ROS水平、抑制血管内皮细胞凋亡有关。     

鸢尾素通过抑制氧化应激减轻高糖/高脂诱导的人脐静脉内皮细胞损伤

目的 研究鸢尾素（irisin）是否通过抑制氧化应激减轻高糖/高脂所致心肌细胞损伤。方法 将培养的人脐静脉内皮细胞（Human umbilical vein endothelial cells,HUVECs）分为3组:正常对照组、高糖/高脂组及高糖/高脂+irisin组。各组培养24 h后检测细胞存活率、凋亡率、ROS产量、NADPH氧化酶gp91phox表达水平。结果 与正常对照组相比,高糖/高脂组细胞存活率显著下降,ROS产量、NADPH氧化酶gp91phox表达水平、细胞凋亡率显著升高(均P<0.05),irisin处理可以逆转上述改变（均P<0.05）。结论 高糖/高脂能够增加人脐静脉内皮细胞氧化应激,促进细胞凋亡;irisin可通过减轻氧化应激而发挥内皮保护作用。     

Apocynin restores endothelial dysfunction in streptozotocin diabetic rats through regulation of nitric oxide synthase and NADPH oxidase expressions

AimIncreased production of reactive oxygen species (ROS) in the diabetic vasculature results in the impairment of nitric oxide (NO)-mediated relaxations leading to impaired endothelium-dependent vasodilation. An important source of ROS is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and the inhibition of this enzyme is an active area of interest. This study aimed to investigate the effects of apocynin, an NADPH oxidase inhibitor, on endothelial dysfunction and on the expression of NO synthase (NOS) and NADPH oxidase in thoracic aorta of diabetic rats.MethodStreptozotocin (STZ)-diabetic rats received apocynin (16 mg/kg per day) for 4 weeks. Endothelium-dependent and -independent relaxations were determined in thoracic aortic rings. Western blotting and RT-PCR analysis were performed for NOSs and NADPH oxidase in the aortic tissue.ResultsAcetylcholine-induced relaxations and l-NAME-induced contractions were decreased in diabetic aorta. The decrease in acetylcholine and l-NAME responses were prevented by apocynin treatment without a significant change in plasma glucose levels. Endothelial NOS (eNOS) protein and mRNA expression exhibited significant decrease in diabetes, while protein and/or mRNA expressions of inducible NOS (iNOS) as well as p22^phox and gp91^phox subunits of NADPH oxidase were increased, and these alterations were markedly prevented by apocynin treatment.ConclusionNADPH oxidase expression is increased in diabetic rat aorta. NADPH oxidase-mediated oxidative stress is accompanied by the decreased eNOS and increased iNOS expressions, contributing to endothelial dysfunction. Apocynin effectively prevents the increased NADPH oxidase expression in diabetic aorta and restores the alterations in NOS expression, blocking the vicious cycle leading to diabetes-associated endothelial dysfunction.     

A novel mechanism of action for statins against diabetes-induced oxidative stress

Aims/hypothesis Atorvastatin exerts beneficial vascular effects in diabetes, but the underlying mechanisms are yet to be elucidated. The aim of the present study was to determine whether Rac-1 is involved in the effect of atorvastatin on oxidative stress and vascular dysfunction. Materials and methods Using human aortic endothelial cells (HAECs) we evaluated the effect of high glucose levels on peroxide production by dihydrodichlorofluorescein and on Rac-1 activity using immunocytochemistry to detect Rac-1 translocation to the membrane. We evaluated vascular function, peroxide production by dihydroethidium and NADPH oxidase activity in vessels from atorvastatin-treated mice. Rac-1 activity was also assessed, both by immunoprecipitation of the Rac–p21-activated kinase complex and by analysis of Rac-1 translocation to the membrane. These experiments were also conducted in vessels infected with an adenoviral vector carrying a constitutively active mutant of Rac-1. Results In HAECs exposed to high glucose levels, atorvastatin prevented oxidative stress, and this protection was associated with impaired Rac-1 activation. This effect was also observed in a murine model of diabetes mellitus. More importantly, the addition of geranylgeranyl pyrophosphate (GGPP) blocked the effects of atorvastatin in both glucose-exposed HAECs and diabetic vessels. Atorvastatin failed to afford protection against vascular abnormalities in the presence of a constitutively active mutant of Rac-1. Conclusions/interpretation The results of this study demonstrate that the vascular antioxidant effect of atorvastatin in diabetes is mediated through inhibition of Rac-1 via a reduction in GGPP. Thus, selective Rac-1 inhibition should be considered in the design of novel pharmacological strategies to reduce the impact of diabetes mellitus on vascular function.     

Reduced silent information regulator 1 signaling exacerbates myocardial ischemia–reperfusion injury in type 2 diabetic rats and the protective effect of melatonin

Diabetes mellitus (DM) increases myocardial oxidative stress and endoplasmic reticulum (ER) stress. Melatonin confers cardioprotective effect by suppressing oxidative damage. However, the effect and mechanism of melatonin on myocardial ischemia–reperfusion (MI/R) injury in type 2 diabetic state are still unknown. In this study, we developed high‐fat diet‐fed streptozotocin (HFD‐STZ) rat, a well‐known type 2 diabetic model, to evaluate the effect of melatonin on MI/R injury with a focus on silent information regulator 1 (SIRT1) signaling, oxidative stress, and PERK/eIF2α/ATF4‐mediated ER stress. HFD‐STZ treated rats were exposed to melatonin treatment in the presence or the absence of sirtinol (a SIRT1 inhibitor) and subjected to MI/R surgery. Compared with nondiabetic animals, type 2 diabetic rats exhibited significantly decreased myocardial SIRT1 signaling, increased apoptosis, enhanced oxidative stress, and ER stress. Additionally, further reduced SIRT1 signaling, aggravated oxidative damage, and ER stress were found in diabetic animals subjected to MI/R surgery. Melatonin markedly reduced MI/R injury by improving cardiac functional recovery and decreasing myocardial apoptosis in type 2 diabetic animals. Melatonin treatment up‐regulated SIRT1 expression, reduced oxidative damage, and suppressed PERK/eIF2α/ATF4 signaling. However, these effects were all attenuated by SIRT1 inhibition. Melatonin also protected high glucose/high fat cultured H9C2 cardiomyocytes against simulated ischemia–reperfusion injury‐induced ER stress by activating SIRT1 signaling while SIRT1 siRNA blunted this action. Taken together, our study demonstrates that reduced cardiac SIRT1 signaling in type 2 diabetic state aggravates MI/R injury. Melatonin ameliorates reperfusion‐induced oxidative stress and ER stress via activation of SIRT1 signaling, thus reducing MI/R damage and improving cardiac function.     

N-乙酰半胱氨酸对糖尿病大鼠心肌NADPH氧化酶和eNOS表达的影响

目的探讨N-乙酰半胱氨酸(NAC)对糖尿病大鼠心肌NADPH氧化酶和内皮一氧化氮合酶(eNOS)表达的影响。方法大鼠随机分为正常对照组、正常对照组NAC治疗组、糖尿病组和糖尿病NAC治疗组。观察8周后测定心肌p22-phox和eNOS蛋白表达水平、血浆和心肌硝酸盐和亚硝酸盐(NOx)水平、血浆总抗氧化物浓度、心肌细胞横截面积和心肌超氧阴离子[O(2-)]水平。结果糖尿病大鼠8周时出现心重/体重和心肌细胞横截面积增加,心肌p22-phox蛋白表达和O(2-)水平显著升高,血浆总抗氧化物浓度降低,心肌eNOS蛋白表达、血浆和心肌NOx水平显著降低。NAC治疗8周能显著逆转糖尿病大鼠上述除心肌NOx外其他各项指标的变化。结论NAC能显著降低糖尿病大鼠心肌氧化应激水平,升高心肌eNOS水平,减轻氧化应激对心肌组织的损伤,产生心脏保护作用。     

Adiponectin protects endothelial cells from the damages induced by the intermittent high level of glucose

Globular adiponectin (gAd) has anti-atherogenic effects on the vascular wall. Intermittent hyperglycemia induces endothelial cells (ECs) injury but the physiological factors that may protect against ECs damage are largely unknown. In the present study, we investigated the effect of gAd on ECs dysfunction induced by intermittent high glucose. The gAd significantly attenuated intermittent high glucose-induced apoptosis and oxidative stress in human umbilical vein endothelial cells. This was achieved by decreasing caspase-3 and 3-nitrotyrosine protein expression, increasing nitric oxide (NO) secretion and phosphorylation of Akt, AMPK, and endothelial nitric oxide synthase protein expression. Pretreatment with a phosphatidylinositol 3' kinase (PI3K) inhibitor, LY294002, partly reversed adiponectin's anti-apoptotic effect. Taken together, our results indicate that gAd acts as a critical physiological factor which protects against fluctuating high glucose-induced endothelial damage. It may act via attenuating apoptosis and increasing synthesis of NO through both the PI3K/AKT and AMPK signaling pathway to reduce oxidative stress and cell apoptosis.     

TIAM1–RAC1 signalling axis-mediated activation of NADPH oxidase-2 initiates mitochondrial damage in the development of diabetic retinopathy

Aims/hypothesis

In diabetes, increased retinal oxidative stress is seen before the mitochondria are damaged. Phagocyte-like NADPH oxidase-2 (NOX2) is the predominant cytosolic source of reactive oxygen species (ROS). Activation of Ras-related C3 botulinum toxin substrate 1 (RAC1), a NOX2 holoenzyme member, is necessary for NOX2 activation and ROS generation. In this study we assessed the role of T cell lymphoma invasion and metastasis (TIAM1), a guanine nucleotide exchange factor for RAC1, in RAC1 and NOX2 activation and the onset of mitochondrial dysfunction in in vitro and in vivo models of glucotoxicity and diabetes.

Methods

RAC1 and NOX2 activation, ROS generation, mitochondrial damage and cell apoptosis were quantified in bovine retinal endothelial cells exposed to high glucose concentrations, in the retina from normal and streptozotocin-induced diabetic rats and mice, and the retina from human donors with diabetic retinopathy.

Results

High glucose activated RAC1 and NOX2 (expression and activity) and increased ROS in endothelial cells before increasing mitochondrial ROS and mitochondrial DNA (mtDNA) damage. N6-[2-[[4-(diethylamino)-1-methylbutyl]amino]-6-methyl-4-pyrimidinyl]-2-methyl-4,6-quinolinediamine, trihydrochloride (NSC23766), a known inhibitor of TIAM1–RAC1, markedly attenuated RAC1 activation, total and mitochondrial ROS, mtDNA damage and cell apoptosis. An increase in NOX2 expression and membrane association of RAC1 and p47^phox were also seen in diabetic rat retina. Administration of NSC23766 to diabetic mice attenuated retinal RAC1 activation and ROS generation. RAC1 activation and p47^phox expression were also increased in the retinal microvasculature from human donors with diabetic retinopathy.

Conclusions/interpretation

The TIAM1–RAC1–NOX2 signalling axis is activated in the initial stages of diabetes to increase intracellular ROS leading to mitochondrial damage and accelerated capillary cell apoptosis. Strategies targeting TIAM1–RAC1 signalling could have the potential to halt the progression of diabetic retinopathy in the early stages of the disease.     

Catechin Averts Experimental Diabetes Mellitus-Induced Vascular Endothelial Structural and Functional Abnormalities

Diabetes mellitus is associated with an induction of vascular endothelial dysfunction (VED), an initial event that could lead to the pathogenesis of atherosclerosis and hypertension. Previous studies showed that catechin, a key component of green tea, possesses vascular beneficial effects. We investigated the effect of catechin hydrate in diabetes mellitus-induced experimental vascular endothelial abnormalities (VEA). Streptozotocin (50 mg/kg, i.p., once) administration to rats produced diabetes mellitus, which subsequently induced VEA in 8 weeks by markedly attenuating acetylcholine-induced endothelium-dependent relaxation in the isolated aortic ring preparation, decreasing aortic and serum nitrite/nitrate concentrations and impairing aortic endothelial integrity. These abnormalities in diabetic rats were accompanied with elevated aortic superoxide anion generation and serum lipid peroxidation in addition to hyperglycemia. Catechin hydrate treatment (50 mg/kg/day p.o., 3 weeks) markedly prevented diabetes mellitus-induced VEA and vascular oxidative stress. Intriguingly, in vitro incubation of L-NAME (100 μM), an inhibitor of nitric oxide synthase, or Wortmannin (100 nM), a selective inhibitor of phosphatidylinositol 3-kinase (PI3K), markedly prevented catechin hydrate-induced improvement in acetylcholine-provoked endothelium-dependent relaxation in the diabetic rat aorta. Moreover, catechin hydrate treatment considerably reduced the elevated level of serum glucose in diabetic rats. In conclusion, catechin hydrate treatment prevents diabetes mellitus-induced VED through the activation of endothelial PI3K signal and subsequent activation of eNOS and generation of nitric oxide. In addition, reduction in high glucose, vascular oxidative stress, and lipid peroxidation might additionally contribute to catechin hydrate-associated prevention of diabetic VEA.     

Pterostilbene Decreases Cardiac Oxidative Stress and Inflammation via Activation of AMPK/Nrf2/HO-1 Pathway in Fructose-Fed Diabetic Rats

Purpose

Oxidative stress has a pivotal role in the pathogenesis of diabetes-associated cardiovascular problems, which has remained a primary cause of the increased morbidity and mortality in diabetic patients. It is of paramount importance to prevent the diabetes-associated cardiac complications by reducing oxidative stress with the help of nutritional or pharmacological agents. Pterostilbene (PT), the primary antioxidant in blueberries, has recently gained attention for its promising health benefits in metabolic and cardiac diseases. However, the mechanism whereby PT reduces diabetic cardiac complications is currently unknown.

Methods

Sprague-Dawley rats were fed with 65% fructose diet with or without PT (20 mg kg^?1 day^?1) for 8 weeks. Heart rate and blood pressure were measured by tail-cuff apparatus. Real-time PCR and western blot experiments were executed to quantify the expression levels of mRNA and protein, respectively.

Results

Fructose-fed rats demonstrated cardiac hypertrophy, hypertension, enhanced myocardial oxidative stress, inflammation and increased NF-κB expression. Administration of PT significantly decreased cardiac hypertrophy, hypertension, oxidative stress, inflammation, NF-κB expression and NLRP3 inflammasome. We demonstrated that PT improved mitochondrial biogenesis as evidenced by increased protein expression of PGC-1α, complex III and complex V in fructose-fed diabetic rats. Further, PT increased protein expressions of AMPK, Nrf2, HO-1 in cardiac tissues, which may account for the prevention of cardiac oxidative stress and inflammation in fructose-fed rats.

Conclusions

Collectively, PT reduced cardiac oxidative stress and inflammation in diabetic rats through stimulation of AMPK/Nrf2/HO-1 signalling.

     

Effect of erythropoietin on endothelial cell apoptosis induced by high glucose

Erythropoietin (Epo) has been reported to inhibit apoptosis of neuron and erythroid cells. In this study, we examined an effect of high glucose on apoptosis of endothelial cells and investigated an anti-apoptotic effect of Epo. Human aortic endothelial cells were incubated with normal or high glucose for 72 h, and apoptotic cells were detected by TUNEL assay. Simultaneously, Epo (100 U/ml) was added to the high glucose medium to examine an inhibitory effect on the apoptosis induced by high glucose. Activity of caspase-3 was also measured using a specific substrate. To investigate a possible mechanism of Epo's action on apoptosis, phosphorylation of Akt was examined by applying Epo. Incubation with high glucose increased apoptosis of endothelial cells, whereas this effect was prevented by co-incubation with Epo. Caspase-3 activity was also increased (1.4-fold) by incubation with high glucose, and the activation of caspase-3 was normalized to the control level by co-incubation with Epo. Furthermore, Epo-induced phosphorylation of Akt in dose-dependent manner. In conclusion, we demonstrated that incubation with high glucose activated caspase-3 and induced apoptosis of endothelial cells. Epo was shown to phosphorylate Akt, leading to the inhibition of caspase-3 activation and apoptosis induced by high glucose. These results suggest that reduced production of Epo in patients with end-stage of nephropathy may accelerate diabetic angiopathy and that replacing therapy with Epo might inhibit endothelial cell apoptosis and diabetic angiopathy.     

阻断肾素-血管紧张素系统对糖尿病大鼠内脏脂肪组织NADPH氧化酶和iNOS表达的影响

阻断糖尿病大鼠肾素血管紧张素系统，可通过下调内脏脂肪组织还原型辅酶Ⅱ氧化酶和诱导型一氧化氮合酶的表达，减少内脏脂肪的氧化应激，改善糖脂代谢和胰岛素抵抗。     

Integrin {alpha}3, but not {beta}1, regulates islet cell survival and function via PI3K/Akt signaling pathways

β1-integrin is a well-established regulator of β-cell activities; however, the role of its associated α-subunits is relatively unknown. Previously, we have shown that human fetal islet and INS-1 cells highly express α3β1-integrin and that collagens I and IV significantly enhance their survival and function; in addition, blocking β1 function in the fetal islet cells decreased adhesion on collagen I and increased apoptosis. The present study investigates the effect of blocking α3. Using α3 blocking antibody or small interfering RNA, the effects of α3-integrin blockade were examined in isolated human fetal or adult islet cells or INS-1 cells, cultured on collagens I or IV. In parallel, β1 blockade was analyzed in INS-1 cells. Perturbing α3 function in human islet or INS-1 cells resulted in significant decreases in cell function (adhesion, spreading, proliferation and Pdx1 and insulin expression/secretion), primarily on collagen IV. A significant decrease in focal adhesion kinase and ERK1/2 phosphorylation and increased caspase3 cleavage were observed on both collagens. These effects were similar to changes after β1 blockade. Interestingly, only α3 blockade reduced expression of phospho-Akt and members of its downstream signaling cascades (glycogen synthase kinase β and X-linked inhibitor of apoptosis), demonstrating a specific effect of α3 on the phosphatidylinositol 3-kinase/Akt pathway. These results suggest that α3- as well as β1-integrin-extracellular matrix interactions are critical for modulating β-cell survival and function through specialized signaling cascades and enhance our understanding of how to improve islet microenvironments for cell-based treatments of diabetes.     

Taurine attenuates acute hyperglycaemia-induced endothelial cell apoptosis, leucocyte-endothelial cell interactions and cardiac dysfunction

OBJECTIVES: Hyperglycaemia is implicated in microvascular inflammatory injury and subsequent cardiac injury/dysfunction. Leucocyte adhesion to the endothelium, migration into tissue and toxic metabolite release are early critical steps. Taurine is a semi-essential amino acid that is endothelial protective and restrains excess leucocyte activity by the formation of less toxic inflammatory mediators. The aim was to establish if taurine reduces acute hyperglycaemia-induced endothelial cell apoptosis and leucocyte interactions and associated cardiac abnormalities. METHODS: Male Sprague-Dawley rats (190-250 g) were randomised to control, hyperglycaemia, and hyperglycaemia plus taurine pre-treated groups. Taurine was gavaged (200 mg/kg body weight) for 5 days. Intravenous hyperglycaemia was established which was 4 times that of baseline for the 3-hour experiment. Using intravital microscopy, mesenteric post-capillary venules were examined for leucocyte rolling, adhesion and migration every 30 min from baseline. Endothelial cell apoptosis and intracellular adhesion molecule (ICAM-1) expression were assessed. In a separate experiment, blood pressure, pulse rate, cardiac injury marker (troponin T), cardiac tissue injury and oedema were also assessed. RESULTS: Hyperglycaemia significantly increased leucocyte adhesion and migration. Blood pressure and troponin T were also elevated significantly. Taurine prevented these cardiac changes, endothelial cell apoptosis and ICAM-1 expression. CONCLUSIONS: Taurine may have a therapeutic role in reducing diabetic microvascular inflammatory injury and concomitant cardiac dysfunction.     

Erythropoietin Attenuates Cardiac Dysfunction in Rats by Inhibiting Endoplasmic Reticulum Stress-Induced Diabetic Cardiomyopathy

Purpose

Enhanced endoplasmic reticulum (ER) stress and down-regulated SERCA2a expression play crucial roles in diabetes. We aimed to verify whether erythropoietin (EPO) attenuates cardiac dysfunction by suppressing ER stress in diabetic rats.

Methods

Forty male SD rats were randomly divided into four groups: control, EPO-treated control, vehicle-treated diabetic, and EPO-treated diabetic groups. The animals in the EPO-treated control and diabetic groups were administered recombinant human EPO (1000 U/kg body weight) once per week for 12 weeks. RT-PCR and Western blotting assays were performed to detect the expression of 78-kDa glucose-regulated protein precursor (GRP78) and sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA2a). We cultured neonatal rat cardiomyocytes and investigated the protective effects of EPO against high glucose (HG)-induced apoptosis. Intracellular calcium levels were measured through confocal microscopy.

Results

We observed increased myocardial GRP78 expression and decreased myocardial SERCA2a expression in diabetic rats. EPO prevented the changes in GRP78, SERCA2a expression and cardiac dysfunction in diabetic rats. The levels of GRP78 protein were significantly reduced in EPO-treated diabetic rats compared with vehicle-treated diabetic rats (GRP78 protein 0.09 ± 0.03 vs. 0.54 ± 0.04, P < 0.01). The levels of the SERCA2a proteins were significantly increased in EPO-treated diabetic rats compared with vehicle-treated diabetic rats (SERCA2a protein 0.60 ± 0.05 vs. 0.13 ± 0.04, P < 0.01). A reduction in apoptosis was observed in the cardiomyocytes treated with 20 U/mL EPO compared with the cardiomyocytes cultured under HG conditions (apoptosis rate 18.9 ± 1.94 vs. 37.9 ± 1.59%, P < 0.01).

Conclusions

This study demonstrates that EPO treatment improved the parameters of cardiac function following HG-induced injury by suppressing ER stress and inducing SERCA2a expression.