Endothelial Dysfunction In Diabetic Rats Research Articles

Quercetin and metformin synergistically reverse endothelial dysfunction in the isolated aorta of streptozotocin-nicotinamide- induced diabetic rats.

The antidiabetic effects of quercetin and metformin are well known. However, their synergistic effect in reversing the symptoms of diabetes-induced endothelial dysfunction remains unknown. In this study, we have investigated their synergistic effect in streptozotocin (STZ)-nicotinamide induced diabetic rats. Seventy-five rats were divided into five groups; normal control, diabetic control, treatment groups (10mg/kg quercetin, 180mg/kg metformin, and combined). The plasma glucose and lipid levels, liver enzymes, ex-vivo studies on aortic rings, histology of liver, kidney, pancreas, abdominal aorta and thoracic aorta, and immunohistochemical studies were carried out. The findings revealed that the combination of quercetin and metformin showed a greater antidiabetic effect than either drug, and rendered protection to the endothelium. The combination effectively reversed the hyperglycemia-induced endothelial dysfunction in diabetic rats. Furthermore, it also reversed the dysregulated expression of eNOS, 3-nitrotyrosine, VCAM-1, CD31 and SIRT-1. Overall, the present study's findings demonstrate that quercetin potentiates the activity of metformin to control the complications associated with diabetes.

Type 2 diabetes progression differently affects endothelial function and vascular contractility in the aorta and the pulmonary artery

Type 2 diabetes (T2D) is associated with cardiovascular and pulmonary disease. How T2D affects pulmonary endothelial function is not well characterized. We investigated the effects of T2D progression on contractility machinery and endothelial function in the pulmonary and systemic circulation and the mechanisms promoting the dysfunction, using pulmonary artery (PA) and aorta. A high-fat (HF, 3 weeks 60% lipid-rich diet) and a high-fat/high-sucrose (HFHSu, combined 60% lipid-rich diet and 35% sucrose during 25 weeks) groups were used as prediabetes and T2D rat models. We found that T2D progression differently affects endothelial function and vascular contractility in the aorta and PA, with the contractile machinery being altered in the PA and aorta in prediabetes and T2D animals; and endothelial function being affected in both models in the aorta but only affected in the PA of T2D animals, meaning that PA is more resistant than aorta to endothelial dysfunction. Additionally, PA and systemic endothelial dysfunction in diabetic rats were associated with alterations in the nitrergic system and inflammatory pathways. PA dysfunction in T2D involves endothelial wall mineralization. The understanding of the mechanisms behind PA dysfunction in T2D can lead to significant advances in both preventative and therapeutic treatments of pulmonary disease-associated diabetes.

Clinacanthus nutans Leaves Extract Reverts Endothelial Dysfunction in Type 2 Diabetes Rats by Improving Protein Expression of eNOS.

Diabetes mellitus is associated with endothelial dysfunction; it causes progressive vascular damage resulting from an impaired endothelium-dependent vasorelaxation. In the diabetes state, presence of hyperglycemia and insulin resistance predisposes to endothelial dysfunction. Clinacanthus nutans, widely used as a traditional medicine for diabetes is reported to have hypoglycemic, hypolipidemic, antioxidant, and anti-inflammatory properties. However, the possibility of C. nutans affecting the vascular endothelial function in diabetes remains unclear. This study was aimed at evaluating the effects of C. nutans methanolic leaves extract (CNME) on endothelial function in a type 2 diabetes (T2DM) rat model. Sixty male Sprague-Dawley rats were divided into five groups (n = 12 per group): nondiabetic control, nondiabetic treated with four weeks of CNME (500 mg/kg/daily), untreated diabetic rats, diabetic treated with metformin (300 mg/kg/daily), and diabetic treated with CNME (500 mg/kg/daily). T2DM was induced by a single intraperitoneal injection of low-dose streptozotocin (STZ) to rats fed with high-fat diet (HFD). Endothelial-dependent and endothelial-independent relaxations and contractions of the thoracic aorta were determined using the organ bath. Aortic endothelial nitric oxide synthase (eNOS) expression was determined using Western blotting. Endothelial-dependent relaxation was reduced in diabetic rats. Both diabetic groups treated with CNME or metformin significantly improved the impairment in endothelium-dependent vasorelaxation; this was associated with increased expression of aortic eNOS protein. CNME- and metformin-treated groups also reduced aortic endothelium-dependent and aortic endothelium-independent contractions in diabetics. Both of these diabetic-treated groups also reduced blood glucose levels and increased body weight compared to the untreated diabetic group. In conclusion, C. nutans improves endothelial-dependent vasodilatation and reduces endothelial-dependent contraction, thus ameliorating endothelial dysfunction in diabetic rats. This may occur due to its effect on increasing eNOS protein expression.

Cardiac dysfunction is attenuated by ginkgolide B via reducing oxidative stress and fibrosis in diabetic rats.

Objective(s):Diabetic cardiomyopathy is a leading factor of high morbidity and mortality in diabetic patients. Our previous results revealed that ginkgolide B alleviates endothelial dysfunction in diabetic rats. This study aimed to investigate the effect of ginkgolide B on cardiac dysfunction and its mechanism in diabetic rats.Materials and Methods:Diabetes was induced in rats through the intraperitoneal injection of streptozotocin (STZ). Hemodynamics was monitored to assess cardiac function. Oxidative stress was examined by detecting levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in serum, and expression of sirtuin (SIRT)1, heme oxygenase (HO)-1, and phosphorylated AMPK in the heart. Masson’s trichrome staining and expression of transforming growth factor (TGF)-β1, smooth muscle actin (α-SMA), and phosphorylated (p-) Smad2 and Smad3 were used to evaluate cardiac fibrosis. Inflammatory cytokine in serum and levels of p-PI3K, p-Akt, p-p38, and p-JNK in the heart were determined.Results:Ginkgolide B significantly improved hemodynamics in diabetic rats. Compared with diabetic rats, treatment with ginkgolide B significantly decreased levels of inflammatory cytokines, improved oxidative stress via reducing MDA concentration, and elevating SOD activity in serum and increasing expression of SIRT1, HO-1, and p-AMPK. Further, ginkgolide B alleviated cardiac fibrosis by decreasing expression of TGF-β1, α-SMA, and p-Smad2 and p-Smad3. Meanwhile, ginkgolide B reduced Levels of p-P38, and p-JNK, and increased levels of p-PI3K and p-Akt.Conclusion:The results suggested that ginkgolide B alleviated cardiac dysfunction by reducing oxidative stress and cardiac fibrosis.

Oleanolic acid alleviates diabetic rat carotid artery injury through the inhibition of NLRP3 inflammasome signaling pathways.

The overexpression of inflammasome components is correlated with diabetes‑associated complications. Oleanolic acid is a triterpenoid compound which is important in arterial injury. The present study evaluated whether oleanolic acid improved diabetic rat carotid artery injury through the inhibition of nucleotide‑binding domain, leucine‑rich‑containing family, pyrin domain‑containing‑3 (NLRP3) inflammasomes signaling pathways. A diabetic rat model was induced using streptozotocin (60mg/kg) and underwent carotid artery injury. Morphometric analysis was performed using hematoxylin and eosin staining. The mRNA and protein levels were assayed by reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. It was found that oleanolic acid (100mg/kg/day) improved body weight, glucose metabolic disorders, neointimal hyperplasia and endothelial dysfunction in diabetic rats with carotid artery injury. In addition, oleanolic acid administration significantly downregulated the mRNA and protein expression levels of endothelin1 in diabetic rats. Oleanolic acid decreased the intimal area and the ratio of neointima to media in diabetic rats. Serum levels of tumor necrosis factor‑α, interleukin(IL)‑1β, IL‑6 and IL‑18 in the oleanolic acid‑treated diabetic rats were downregulated. Consistent with the serum results, it was demonstrated that oleanolic acid administration caused a significant decrease in the levels of NLRP3, caspase‑1 and IL‑1β in the carotid arteries of diabetic rats. Taken together, these observations suggested that oleanolic acid attenuated carotid artery injury in diabetic rats and the underlying mechanism was mediated, at least partially, through the suppression of NLRP3 inflammasome signaling pathways.

Administration of Selenium Decreases Lipid Peroxidation and Increases Vascular Endothelial Growth Factor in Streptozotocin Induced Diabetes Mellitus.

The imbalance in oxidant/antioxidant status plays a pivotal role in diabetes mellitus (DM). Selenium is a integral component of the antioxidant enzyme glutathione peroxidase. Se treatment induces angiogenesis and improves endothelial function through increased expression of vascular endothelial growth factor (VEGF). The aim of this study is to investigate the effect of selenium on oxidative stress, VEGF, and endothelin 1 (ET1) in a DM rat model. We performed an experimental animal study with 64 adult male Wistar-Albino rats. Rats were divided into the following groups (n=8): control (C)7, C21, C+sodium selenite (Se)7, and C+Se21 (control rats), and DM7, DM21, DM+Se7, and DM+Se21 (diabetic rats). Diabetes was induced by 2-deoxy-2-(3-methyl-3-nitrosoureido)- D-glucopyranose [streptozotocin (STZ)]. Three weeks after STZ, DM+Se7 rats received intraperitoneal (i.p.) injections of 0.4 mg/kg Se for 7 days. The DM+Se21 rats received these injections for 21 days. The same dose/duration of Se was administered to the C+Se7 and C+Se21 groups. The remaining rats (C7, C21, DM7, DM21) received physiologic saline injections for 7 or 21 days. Ferric reducing antioxidant power (FRAP), malondialdehyde (MDA), advanced oxidation protein products (AOPP), and endothelial function markers (VEGF and ET1) in plasma samples were measured. Diabetic rats (DM7 and DM21) had significantly increased plasma FRAP (P=0.002, P=0.001), AOPP (P=0.024, P=0.01), MDA (P=0.004, P=0.001), and ET1 (P=0.028, P=0.003) levels compared with C7 and C21 control rats. VEGF (P=0.02, P=0.01) significantly decreased in DM7 and DM21 diabetic rats compared with their controls (C7, C21). Se administration reversed the increased MDA and decreased VEGF levels, and lowered plasma glucose levels in the DM+Se7 and DM+Se21 diabetic groups compared with diabetic rats (DM7, DM21). We observed positive correlations between FRAP-AOPP (r=0.460), FRAP-ET1 (r=0.510), AOPP-MDA (r=0.270), and AOPP-ET1 (r=0.407), and a negative correlation between MDA-VEGF (r=-0.314). We observed accentuated oxidative stress and impaired endothelial function in diabetes. Se treatment reduced lipid peroxidation and hyperglycemia. Se probably improved endothelial dysfunction in diabetic rats because of the increased VEGF levels.

The impact of exogenous estrogens on biochemical markers of endothelial dysfunction in diabetic rats with hypoestrogenia

It was investigated the impact of selective estrogen receptor modulator PE0607 comparing to 17β-estradiol on the biochemical markers of endothelial dysfunction in ovariectomized rats with type 2 diabetes. It was established that injection of PE0607 as well as 17β-estradiol decreases lipid peroxidation first products in serum and increases serum whole antioxidant activity and NO-synthase activity in vessels of experimental rats. These results justify the perspectives of compound PE0607 use as a potential gender-specific agent for prevention and treatment of diabetic cardiovascular disorders in women with hypoestrogenia.

A comprehensive review of the pharmacodynamics of the SGLT2 inhibitor empagliflozin in animals and humans.

Empagliflozin (formerly known as BI 10773) is a potent, competitive, and selective inhibitor of the sodium glucose transporter SGLT2, which mediates glucose reabsorption in the early proximal tubule and most of the glucose reabsorption by the kidney, overall. Accordingly, empagliflozin treatment increased urinary glucose excretion. This has been observed across multiple species including humans and was reported under euglycemic conditions, in obesity and, most importantly, in type 2 diabetic patients and multiple animal models of type 2 diabetes and of type 1 diabetes. This led to a reduction in blood glucose, smaller blood glucose excursions during oral glucose tolerance tests, and, upon chronic treatment, a reduction in HbA1c in animal models and patients. In rodents, such effects were observed in early and late phases of experimental diabetes and were associated with preservation of pancreatic β-cell function. Combination studies in animals demonstrated that beneficial metabolic effects of empagliflozin may also manifest when added to other types of anti-hyperglycemic treatments including linagliptin and pioglitazone. While some anti-hyperglycemic drugs lead to weight gain, empagliflozin treatment was associated with reduced body weight in normoglycemic obese and non-obese animals despite an increased food intake, largely due to a loss of adipose tissue; on the other hand, empagliflozin preserved body weight in models of type 1 diabetes. Empagliflozin improved endothelial dysfunction in diabetic rats and arterial stiffness, reduced blood pressure in diabetic patients, and attenuated early signs of nephropathy in diabetic animal models. Taken together, the SGLT2 inhibitor empagliflozin improves glucose metabolism by enhancing urinary glucose excretion; upon chronic administration, at least in animal models, the reductions in blood glucose levels are associated with beneficial effects on cardiovascular and renal complications of diabetes.

Ginkgolide B increases hydrogen sulfide and protects against endothelial dysfunction in diabetic rats.

AimTo evaluate the effect of ginkgolide B treatment on vascular endothelial function in diabetic rats.MethodsThe study included four groups with 15 male Sprague-Dawley rats: control group; control group treated with ginkgolide B; diabetic group; and diabetic treated with ginkgolide B. The activity of superoxide dismutase (SOD), malondialdehyde content, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, and glutathione peroxidase 1 (GPX1) protein expression were determined in aortic tissues. Vasoconstriction to phenylephrine (PHE) and vasorelaxation to acetylcholine (Ach) and sodium nitroprusside (SNP) were assessed in aortic rings. Nitric oxide (NO) and hydrogen sulfide (H2S) were measured, as well as cystathionine γ lyase (CSE) and cystathionine β synthetase (CBS) protein expression, and endothelial nitric oxide synthase (eNOS) activity.ResultsDiabetes significantly impaired PHE-induced vasoconstriction and Ach-induced vasorelaxation (P < 0.001), reduced NO bioavailability and H2S production (P < 0.001), SOD activity, and GPX1 protein expression (P < 0.001), and increased malondialdehyde content and NADPH oxidase subunits, and CSE and CBS protein expression (P < 0.001). Ginkgolide B treatment improved PHE vasoconstriction and Ach vasorelaxation (P < 0.001), restored SOD (P = 0.005) and eNOS (P < 0.001) activities, H2S production (P = 0.044) and decreased malondialdehyde content (P = 0.014). Vasorelaxation to SNP was not significantly different in control and diabetic rats with or without ginkgolide B treatment. Besides, ginkgolide B increased GPX1 protein expression and reduced NADPH oxidase subunits, CBS and CSE protein expression.ConclusionGinkgolide B alleviates endothelial dysfunction by reducing oxidative stress and elevating NO bioavailability and H2S production in diabetic rats.

Abstract 12503: Synchrotron Radiation Coronary Microangiography for Evaluating Changes in the Caliber of the in vivo Rat Coronary Artery After Endothelin Administration

Background: Conventional coronary angiography can visualize vessels of 300 μm in diameter, but not those of smaller diameter, such as the proliferating collateral arteries of ischemic heart disease and the new blood vessels formed in regenerative medicine. We have developed a system of synchrotron radiation coronary microangiography (SRCA) in the in vivo rat. The purpose of this study was to define the minimum detectable caliber change in the coronary arteries of the in vivo rat by inducing vasoconstriction with endothelin during SRCA. Method: SRCA was performed at the Photon Factory of the High Energy Accelerator Research Organization (Tsukuba, Japan). The advantages of synchrotron radiation derived X-rays are high spatial resolution (5 μm/pixel) due to increased photon density and straightness of beam. High density resolution is obtained with a high-gain avalanche rushing amorphous photoconductor camera using a fiber-optic plate. Rats were anesthetized. The polyethylene tube for angiography was inserted into the carotid artery. SRCA was performed before and after endothelin administration. Results: The electrocardiography showed ST elevation after endothelin administration. High spatial and density resolution images were obtained. Figures A and B show the changes in the caliber of the coronary arteries: Figure A shows the arteries before endothelin administration, and Figure B shows them after endothelin administration. The minimum identified coronary artery diameter in the in vivo rat was 65 μm, and the minimum detectable caliber change was 20 μm. Conclusion: The SRCA system could confirm the microvascular constriction of the coronary arteries in the in vivo rat after endothelin administration. We plan next to use SRCA to evaluate endothelial dysfunction in diabetic rats. SRCA may aid investigation of collateral artery proliferation in ischemic heart disease and new blood vessel formation in regenerative medicine in the near future.

Ferulic acid combined with astragaloside IV protects against vascular endothelial dysfunction in diabetic rats.

Dysfunction of the endothelium is regarded as an important factor in the pathogenesis of vascular disease in diabetes mellitus (DM). Unfortunately, prevention of the progression of vascular complications of DM remains pessimistic. Ferulic acid and astragaloside IV, isolated from traditional Chinese medicine Angelica sinensis and Radix astragali respectively, exhibit potential cardio-protective and anti-hyperglycemic properties. In the present study, we investigated the protective effects and underlying mechanism of ferulic acid and astragaloside IV against vascular endothelial dysfunction in diabetic rats. After the diabetic rat model was established using streptozotocin, sixty rats were divided into 6 groups (control, model, ferulic acid, astragaloside IV, ferulic acid + astragaloside IV, and metformin) and treated for 10 weeks. Blood samples were collected to measure levels of hemoglobin A1c (HbAlc), triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), low density lipoproteins (Ox-LDL), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatinine (Cr), nitric oxide (NO) and endothelial nitric oxide synthase (eNOS), and abdominal aorta tissue samples were collected for observing histological morphology changes of endothelium and detecting gene and protein expression of nuclear factor-κB (NF-κB) P65, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor α (TNF-α). We found that ferulic acid combined with astragaloside IV was capable of improving the structure of the aortic endothelium wall, attenuating the increase of HbAlc, TG, TC, LDL-C and Ox-LDL, promoting the release of NO and eNOS, and inhibiting over-activation of MCP-1, TNF-α, and NF-κB P65, without damage to liver and kidney function. In conclusion, ferulic acid combined with astragaloside IV exhibited significant protective effects against vascular endothelial dysfunction in diabetic rats through the NF-κB pathway involving decrease of Ox-LDL, increase of NO and eNOS, and activation of NF-κB P65, MCP-1 and TNF-α.

Effects of erythritol on endothelial function in patients with type 2 diabetes mellitus: a pilot study

Sugar substitutes are important in the dietary management of diabetes mellitus. Erythritol is a non-caloric dietary bulk sweetener that reverses endothelial dysfunction in diabetic rats. We completed a pilot study to examine the effects of erythritol on vascular function in patients with type 2 diabetes mellitus. Participants (n=24) consumed erythritol 36g/day as an orange-flavored beverage for 4weeks and a single dose of 24g during the baseline and final visits. We assessed vascular function before and after acute (2h) and chronic (4weeks) erythritol consumption. Acute erythritol improved endothelial function measured by fingertip peripheral arterial tonometry (0.52±0.48 to 0.87±0.29au, P=0.005). Chronic erythritol decreased central pulse pressure (47±13 to 41±9mmHg, P=0.02) and tended to decrease carotid-femoral pulse wave velocity (P=0.06). Thus, erythritol consumption acutely improved small vessel endothelial function, and chronic treatment reduced central aortic stiffness. Erythritol may be a preferred sugar substitute for patients with diabetes mellitus.

Chronic treatment with d-chiro-inositol prevents autonomic and somatic neuropathy in STZ-induced diabetic mice

D-chiro-inositol (DCI) has been shown to prevent and reverse endothelial dysfunction in diabetic rats and rabbits. The present study evaluates the preventive effect of DCI on experimental diabetic neuropathy (DN). Streptozotocin-induced (STZ) diabetic mice were treated by oral gavage for 60 days with DCI (20 mg/kg/12 h) or saline (NaCl 0.9%; 0.1 ml/10 g/12 h; Diab) and compared with euglycaemic groups treated with saline (0.1 ml/10 g/12 h; Eugly). We compared the response of the isolated sciatic nerve, corpora cavernosa or vas deferens to electrical stimulation. The electrically evoked compound action potential of the sciatic nerve was greatly blunted by diabetes. The peak-to-peak amplitude (PPA) was decreased from 3.24 ± 0.7 to 0.9 ± 0.2 mV (p < 0.05), the conduction velocity (CV) of the first component was reduced from 46.78 ± 4.5 to 26.69 ± 3.8 ms (p < 0.05) and chronaxy was increased from 60.43 ± 1.9 to 69.67 ± 1.4 ms (p < 0.05). These parameters were improved in nerves from DCI-treated mice (p < 0.05). PPA in the DCI group was 5.79 ± 0.8 mV (vs. 0.9 ± 0.2 mV-Diab; p < 0.05) and CV was 45.91 ± 3.6 ms (vs. 26.69 ± 3.8 ms-Diab; p < 0.05). Maximal relaxation of the corpus cavernosum evoked by electrical stimulation (2-64 Hz) in the Diab group was 36.4 ± 3.8% compared to 65.4 ± 2.8% in Eugly and 59.3 ± 5.5% in the DCI group (p < 0.05). Maximal contraction obtained in the vas deferens was 38.0 ± 9.2% in Eugly and 11.5 ± 2.6% in Diab (decrease of 69.7%; p < 0.05), compared to 25.2 ± 2.3% in the DCI group (p < 0.05 vs. diabetic). Electron microscopy of the sciatic nerves showed prevention of neuronal damage. DCI has a neuroprotective action in both autonomic and somatic nerves in STZ-induced DN.

Ameliorative effect of berberine on endothelial dysfunction in diabetic rats induced by high-fat diet and streptozotocin

Berberine can improve insulin resistance, lower blood glucose, and regulate lipid metabolism disorders which cause endothelial dysfunction, leading to vascular complications of type 2 diabetes mellitus. The aim of the present study was to investigate the effects of berberine on endothelial dysfunction of aortas in type 2 diabetes mellitus rats and its mechanism. Wistar rats were randomly divided into four groups: diabetic rats, control rats, diabetic rats treated with berberine (100 mg/kg), and control rats treated with berberine. The serum fasting blood glucose, insulin, total cholesterol, triglyceride and nitric oxide (NO) levels were tested. Acetylcholine-induced endothelium-dependent relaxation and sodium nitroprusside induced endothelium-independent relaxation were measured in aortas for estimating endothelial function. The expression of endothelial nitric oxide synthase (eNOS) mRNA was measured by RT-PCR, and the protein expressions of eNOS and NADPH oxidase (NOX4) were analyzed by western blot. The results showed that berberine significantly decreased fasting blood glucose, and triglyceride levels in diabetic rats. Berberine also improved endothelium-dependent vasorelaxation impaired in aorta. The expressions of eNOS mRNA and protein were significantly increased, while NOX4 protein expression was decreased in aortas from diabetic rats with berberine treatment. Moreover, serum NO levels were elevated after berberine treatment. In conclusion, berberine restores diabetic endothelial dysfunction through enhanced NO bioavailability by up-regulating eNOS expression and down-regulating expression of NADPH oxidase.

Hyperresponsiveness to serotonin in rat pulmonary arteries from rats with streptozotocin–induced diabetes

Recent data suggest that diabetes is a risk factor for pulmonary hypertension. Several lines of evidence suggest that serotonin is a pathogenetic factor in pulmonary hypertension. We have also recently found pulmonary endothelial dysfunction in diabetic rats. The aim of the present study was to analyze whether diabetes induces changes in the response to serotonin in rat pulmonary arteries and the mechanisms involved. Male Sprague‐Dawley rats were randomly divided into a control (saline) and a diabetic group (70 mg/kg streptozotocin). After 6 weeks, the responses to serotonin were enhanced in pulmonary arteries from diabetic rats. This hyperresponsiveness was endothelium‐independent and unaffected by inhibition of NO synthase but prevented by the cyclooxygenase (COX) inhibitor indomethacin, by superoxide dismutase and by the NADPH oxidase inhibitor apocynin. Lungs from diabetic animals showed an increased expression of COX‐2 as measured by Western blot analysis. In conclusion, as has been described in animal models of pulmonary hypertension, pulmonary arteries from diabetic animals show hyperresposiveness to serotonin. This effect appears to be related to COX‐2 derived metabolites and NADPH oxidase‐induced superoxide production. Supported by Comisi ón Interministerial de Ciencia y Tecnología (CICYT SAF2008‐03948).

Cilostazol Activates AMP-activated Protein Kinase and Restores Endothelial Function in Diabetes

Endothelial dysfunction plays a key role in atherogenesis. We investigated whether AMP-activated protein kinase (AMPK) activity is a downstream mediator of the beneficial effects of cilostazol on vascular endothelial cells and whether cilostazol might reverse endothelial dysfunction in diabetic rats. Treatment of human umbilical vein endothelial cells (HUVECs) with cilostazol resulted in time-dependent activation of AMPK, as monitored by phosphorylation of AMPK and its down-stream target, acetyl-CoA carboxylase (ACC). Activation of AMPK by cilostazol was through signaling pathway independent of cyclic AMP and caused phosphorylation of endothelial nitric oxide synthase (eNOS), leading to increased production of nitric oxide (NO), while inhibiting cytokine-induced nuclear factor-kappaB (NF-kappaB) activation, leading to suppression of VCAM-1 gene expression. Significantly reduced eNOS activity and NO production in response to cilostazol and attenuation of cilostazol-induced inhibition of NF-kappaB activation were observed in cells treated with AMPK siRNA. We also demonstrated that administration of cilostazol to diabetic rats significantly restored endothelium-dependent vasodilation. Furthermore, treatment of diabetic rats with cilostazol increased tetrahydrobiopterin (BH4) levels in the aorta. Thus, recovery of BH4 following administration of cilostazol might also contribute to restoration of endothelial function in diabetic rats. Our findings suggest that the beneficial effects of cilostazol on endothelial function may be due to AMPK activation. Restoration of endothelial dysfunction in diabetic rats by cilostazol is at least partly attributed to amelioration of biopterin metabolism in the aorta.

Carvedilol ameliorates endothelial dysfunction in streptozotocin-induced diabetic rats

The beta-blocker, carvedilol has an additional endothelium-dependent vasodilating properties in patients with hypertension or heart failure. Whether carvedilol can improve endothelium-dependent relaxation in a diabetic animal model and its mechanism of action are unknown. The aim of this study was to investigate the effect of carvedilol on the endothelial-response of aortas from diabetic rats and the underlying mechanism. Acetylcholine-induced endothelium-dependent relaxation, sodium nitroprusside (SNP)-induced endothelium-independent relaxation, and expression of nitric oxide synthase 3 (NOS3) mRNA were measured in aortas isolated from both non-diabetic and streptozotocin-induced diabetic rats. The level of NO in serum was also measured 5 weeks after carvedilol administration (1 or 10 mg/kg/day). Endothelium-dependent relaxation declined along with the decrease of serum NO level in aortas from diabetic rats. Treatment with carvedilol for 5 weeks prevented the inhibition of endothelium-dependent relaxation and the decrease of serum NO levels caused by diabetes. The expression of NOS3 mRNA, protein expression and NOS3 phosphorylation at Ser1177 in diabetic rat aorta was very low in untreated diabetic aortas compared with the healthy group. Administration of carvedilol not only significantly increased the expression of NOS3 mRNA but also protein expression and NOS3 phosphorylation at Ser1177 in the healthy and diabetic groups. In conclusion, chronic carvedilol administration significantly ameliorated the endothelial dysfunction in diabetic rat aortas, in which increased NO level, up-regulated NOS3 mRNA and phosphorylation at Ser1177 may be involved.

P142. Effect of sarpogrelate HCl, a selective 5-HT2A antagonist, on endothelial dysfunction in diabetic rats

P142. Effect of sarpogrelate HCl, a selective 5-HT2A antagonist, on endothelial dysfunction in diabetic rats

Protective Effect of Exercise Training plus Vitamin C supplementation on Endothelial Dysfunction in Diabetic Rats

PURPOSE: To determine the protective effects of exercise training plus vitamin c supplementation on diabetic endothelial dysfunction (ED). METHODS: Male Spraque-Dawley rats (n=28) were divided into four groups; control (Con), diabetes (DM), diabetes with exercise training (DM+Ex) and diabetes with exercise training plus supplemented vitamin c (DM+Ex+Vit.c). Diabetes was induced by intravenous injection of streptozotocin (STZ;50 mg/kgBW). The exercise training protocol consisted of treadmill running 5 times/week with velocity 13–15 m/min for 30 min. Vitamin c was given in drinking water with the concentration of 1 g/L. To examine ED, leukocyte adhering in mesenteric venules and vascular reactivity response to the endothelial cell-dependent vasodilator, Ach in mesenteric arterioles were monitored using intravital fluorescence microscopy. Muscle malondialdehyde level (MDA) and activity of superoxide dismutase (SOD) as well as endothelial nitric oxide synthase protein level (eNOS) in heart was also measured. RESULTS: At 24- wk, the diabetic state enhanced leukocyte adhesion (5.57+0.97 vs 11.86+0.86 cells/100 um) and impaired vasorelaxation (12.59+1.45 vs 3.24+0.51 %). The increase of leukocyte adherence was attenuated in both DM+Ex (5.13+0.70 cells/100 um, P < 0.001) and DM+Ex+Vit.c (5.14 +0.67 cells/100 um, P < 0.001). However, the impaired vasorelaxation was found to be increased in only DM+Ex+Vit. c (9.62+1.66 %, P < 0.05). MDA of DM+Ex (2437.43+251.55 nmole/g wet wt.) and DM+Ex+Vit.c (1947.38+143.57 nmole/g wet wt.) were significantly lower (P < 0.01) than those of DM (2843.83+286.42 nmole/g wet wt.). DM had significantly lower in SOD (P < 0.05) than Con but there were no significant differences in SOD activity among DM+Ex, DM+Ex+Vit.c and Con. It failed to improve the decreased eNOS in DM+Ex (1.57 +0.81 ug /5μg Protein) but not in DM+Ex+Vit.c (4.35 +0.40 ug /5μg Protein, P < 0.05) when compared with DM (1.45 +0.66 ug /5μg Protein). CONCLUSION: Regular exercise training combined with vitamin c supplementation is an effective therapeutic modality to prevent diabetic endothelial dysfunction by ameliorating the diabetic-induced imbalance of oxidants/antioxidants.