Endothelial Dysfunction In Diabetes Mellitus Research Articles

Oxidative Stress, Endothelial Dysfunction, and N-Acetylcysteine in Type 2 Diabetes Mellitus.

Significance: Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality globally. Endothelial dysfunction is closely associated with the development and progression of CVDs. Patients with diabetes mellitus (DM) especially type 2 DM (T2DM) exhibit a significant endothelial cell (EC) dysfunction with substantially increased risk for CVDs. Recent Advances: Excessive reactive oxygen species (ROS) and oxidative stress are important contributing factors to EC dysfunction and subsequent CVDs. ROS production is significantly increased in DM and is critically involved in the development of endothelial dysfunction in diabetic patients. In this review, efforts are made to discuss the role of excessive ROS and oxidative stress in the pathogenesis of endothelial dysfunction and the mechanisms for excessive ROS production and oxidative stress in T2DM. Critical Issues: Although studies with diabetic animal models have shown that targeting ROS with traditional antioxidant vitamins C and E or other antioxidant supplements provides promising beneficial effects on endothelial function, the cardiovascular outcomes of clinical studies with these antioxidant supplements have been inconsistent in diabetic patients. Future Directions: Preclinical and limited clinical data suggest that N-acetylcysteine (NAC) treatment may improve endothelial function in diabetic patients. However, well-designed clinical studies are needed to determine if NAC supplementation would effectively preserve endothelial function and improve the clinical outcomes of diabetic patients with reduced cardiovascular morbidity and mortality. With better understanding on the mechanisms of ROS generation and ROS-mediated endothelial damages/dysfunction, it is anticipated that new selective ROS-modulating agents and effective personalized strategies will be developed for the management of endothelial dysfunction in DM.

Glycemic Variability and Its Correlation with Large for Gestation-age Babies in Gestational Diabetic Pregnancies.

Although glycemic variability (GV) has been shown to be associated with endothelial dysfunction in diabetes mellitus (DM), there is a dearth of literature on its correlation in gestational diabetic pregnancies. To compare GV and 24-hour ambulatory glucose profile (AGP) in gestational diabetic pregnancies with and without large for gestation-age (LGA) babies. It was a cross-sectional observational study. A total of 40 pregnant females between 19 and 35 years with gestational DM (GDM) controlled on pharmacotherapy fulfilling inclusion criteria were recruited. A flash glucose monitor (FGM) was used to record AGP between 32 and 36 weeks of gestation in these women. A total of 400 patient days with 38,400 glucose values in the study group were analyzed. Various glucose measures were compared between the GDM pregnancies with or without LGA babies. The incidence of LGA was 15% in these pregnant women who were on pharmacotherapy and apparently controlled as evidenced by self-monitoring of blood sugar values. All the parameters of 24-hour AGP except dinner values were significantly high in the LGA group when compared with the non-LGA group [mean amplitude of glycemic excursion (MAGE) LGA vs non-LGA 74.58 ± 16.83 vs 49.86 ± 12.83 mg/dL, p = 0.002; standard deviation (SD) LGA vs non-LGA 30.19 ± 9.69 vs 20.10 ± 5.97 mg/dL, p = 0.001]. Variables of GV: MAGE and SD were significantly high in the LGA group (p < 0.001). Time below range (TBR) and time above range (TAR) were also significantly altered in the LGA group (p < 0.001). High GV and time in the range are the important parameters that can be well correlated with LGA babies in gestational diabetic pregnancies on pharmacotherapy. An FGM is a good monitoring device to measure this parameter and can be used as an adjunct to modify measures to control the glucose values within range in these pregnancies.

Mechanism of the antidiabetic action of Nigella sativa and Thymoquinone: a review.

Long used in traditional medicine, Nigella sativa (NS; Ranunculaceae) has shown significant efficacy as an adjuvant therapy for diabetes mellitus (DM) management by improving glucose tolerance, decreasing hepatic gluconeogenesis, normalizing blood sugar and lipid imbalance, and stimulating insulin secretion from pancreatic cells. In this review, the pharmacological and pharmacokinetic properties of NS as a herbal diabetes medication are examined in depth, demonstrating how it counteracts oxidative stress and the onset and progression of DM. This literature review drew on databases such as Google Scholar and PubMed and various gray literature sources using search terms like the etiology of diabetes, conventional versus herbal therapy, subclinical pharmacology, pharmacokinetics, physiology, behavior, and clinical outcomes. The efficiency and safety of NS in diabetes, notably its thymoquinone (TQ) rich volatile oil, have drawn great attention from researchers in recent years; the specific therapeutic dose has eluded determination so far. TQ has anti-diabetic, anti-inflammatory, antioxidant, and immunomodulatory properties but has not proved druggable. DM's intimate link with oxidative stress, makes NS therapy relevant since it is a potent antioxidant that energizes the cell's endogenous arsenal of antioxidant enzymes. NS attenuates insulin resistance, enhances insulin signaling, suppresses cyclooxygenase-2, upregulates insulin-like growth factor-1, and prevents endothelial dysfunction in DM. The interaction of NS with mainstream drugs, gut microbiota, and probiotics opens new possibilities for innovative therapies. Despite its strong potential to treat DM, NS and TQ must be examined in more inclusive clinical studies targeting underrepresented patient populations.

Pathophysiological correlation of arginase-1 in development of type 2 diabetes from obesity in adolescents

BackgroundThere is great interest to understand causal pathophysiological correlation between obesity and diabetes mellitus (DM). Vascular endothelial dysfunction is crucially involved in pathogenesis of vascular complications in DM. Recently, increased arginase expression and activity have been described as underlying mechanisms of endothelial dysfunction in DM and vascular inflammation in obesity. By limiting L-arginine bioavailability to endothelial nitric oxide synthase (NOS III), nitric oxide production is potentially impaired. MethodsWe investigated the impact of plasma from diabetic and obese adolescents on arginase and NOS III expression in cultured human endothelial cells (ECs). A total of 148 male adolescents participated in this study including 18 obese, 28 type 1-, 28 type 2-DM patients, and 74 age-matched healthy volunteers. ResultsA concurrent increase in arginase-1 (1.97-fold) and decrease in NOS III expression (1.45-fold) was observed in ECs exposed to type 2 diabetic plasma compared to control subjects. ECs incubated with type 1 DM plasma had a diminished NOS III level without impact on arginase-1 expression. Urea-assay featured an increased arginase activity in treated ECs with type 1- or 2-DM plasma. Despite increased pro-inflammatory cytokines and chemokines in obese plasma, arginase-1 expression/activity did not change in treated ECs. However, NOS III expression was significantly reduced. Pearson analysis revealed positive correlation between arginase-1, but not NOS III, expression with FBS in ECs treated with type 2-DM plasma. ConclusionsOur data demonstrate that increased arginase-1 expression/activity in ECs, as critical pathogenic factor is correlated with development of obesity-related type 2-DM and linked vascular disease.

2 типті қант диабеті бар науқастарда эндотелиальды дисфункциямен байланысты тамырлы асқынулар

This article presents information on diabetes mellitus and its complications and its relationship with the mechanism of endothelial dysfunction based on previous studies. Type 2 diabetes is a chronic disease that significantly increases the risk of cardiovascular complications. Endothelial dysfunction is considered an early indicator of the diagnosis of diabetic vascular complications. Although the exact pathogenetic mechanisms of ED in diabetes mellitus are still unclear, at the initial stage it turned out that they trigger the synthesis of nitric oxide, oxidative phosphorylation of mitochondria, and other processes. The subsequent main factors influencing the activation of this process are dyspledemia, oxidative processes, and inflammation. The paper considers current literature data on hyperglycemia, oxidative stress, and glycation end products with endothelial changes. A separate section is devoted to oxidative stress and their significance in the development of endothelial dysfunction in diabetes mellitus. In addition, in this review, special attention is paid to the main mechanisms involved in the occurrence of endothelial dysfunction, the production of large amounts of reactive oxygen species (ROS), inflammation, as well as their relationship with the main factors of cardiovascular risk.

Molecular mechanisms of coronary microvascular endothelial dysfunction in diabetes mellitus: focus on mitochondrial quality surveillance.

Coronary microvascular endothelial dysfunction is both a culprit and a victim of diabetes, and can accelerate diabetes-related microvascular and macrovascular complications by promoting vasoconstrictive, pro-inflammatory and pro-thrombotic responses. Perturbed mitochondrial function induces oxidative stress, disrupts metabolism and activates apoptosis in endothelial cells, thus exacerbating the progression of coronary microvascular complications in diabetes. The mitochondrial quality surveillance (MQS) system responds to stress by altering mitochondrial metabolism, dynamics (fission and fusion), mitophagy and biogenesis. Dysfunctional mitochondria are prone to fission, which generates two distinct types of mitochondria: one with a normal and the other with a depolarized mitochondrial membrane potential. Mitochondrial fusion and mitophagy can restore the membrane potential and homeostasis of defective mitochondrial fragments. Mitophagy-induced decreases in the mitochondrial population can be reversed by mitochondrial biogenesis. MQS abnormalities induce pathological mitochondrial fission, delayed mitophagy, impaired metabolism and defective biogenesis, thus promoting the accumulation of unhealthy mitochondria and the activation of mitochondria-dependent apoptosis. In this review, we examine the effects of MQS on mitochondrial fitness and explore the association of MQS disorders with coronary microvascular endothelial dysfunction in diabetes. We also discuss the potential to treat diabetes-related coronary microvascular endothelial dysfunction using novel MQS-altering drugs.

Overexpression of E3 ubiquitin ligase Cbl attenuates endothelial dysfunction in diabetes mellitus by inhibiting the JAK2/STAT4 signaling and Runx3-mediated H3K4me3

BackgroundDiabetes mellitus (DM), a most common chronic disease, is featured with impaired endothelial function and bioavailability of nitric oxide (NO), while E3 ubiquitin ligase appears to alleviate endothelial dysfunction as a promising option for DM treatment. Herein, we aimed to determine whether E3 ubiquitin ligase casitas B-lineage lymphoma (Cbl) alleviates endothelial dysfunction in DM rats by JAK2/STAT4 pathway.MethodsA rat model of DM was developed through intraperitoneal injection of streptozotocin, followed by collection of aortic tissues to determine the expression of Cbl, JAK2, runt-related transcription factor 3 (Runx3) and STAT4. Human umbilical vein endothelial cells (HUVECs) were cultured in high glucose (HG) condition to induce DM as an in vitro model. With gain- and loss-function method, we assessed the aberrantly expressed Cb1 on endothelial dysfunction, NO production and apoptosis of HUVECs.ResultsCbl was reduced in DM rat tissues and HG-induced HUVECs, where JAK2, Runx3 and STAT4 were elevated. It was found that overexpression of Cbl alleviated endothelial dysfunction by increasing NO production and restoring vasodilation and suppressing apoptosis of HUVECs. Mechanistically, Cb1 enhanced JAK2 ubiquitination and decreased JAK2 and STAT4 expression, where STAT4 improved Runx3 expression by regulating histone H3 lysine 4 trimethylation level. Overexpression of JAK2 and STAT4, or Runx3 increased apoptosis of HUVECs, abrogating the effect of Cb1 on endothelial function.ConclusionIn conclusion, Cbl alleviates endothelial dysfunction by inactivation of the JAK2/STAT4 pathway and inhibition of Runx3 expression in DM. These evidence might underlie novel Cbl-based treatment against DM in the future.

Sitagliptin attenuates endothelial dysfunction independent of its blood glucose controlling effect

Although the contributions of sitagliptin to endothelial dysfunction in diabetes mellitus were previously reported, the mechanisms still undefined. Autophagy plays an important role in the development of diabetes mellitus, but its role in diabetic macrovascular complications is unclear. This study aims to observe the effect of sitagliptin on macrovascular endothelium in diabetes and explore the role of autophagy in this process. Diabetic rats were induced through administration of high-fat diet and intraperitoneal injection of streptozotocin. Then diabetic rats were treated with or without sitagliptin for 12 weeks. Endothelial damage and autophagy were measured. Human umbilical vein endothelial cells were cultured either in normal glucose or in high glucose medium and intervened with different concentrations of sitagliptin. Rapamycin was used to induce autophagy. Cell viability, apoptosis and autophagy were detected. The expressions of proteins in c-Jun N-terminal kinase (JNK)-Bcl-2-Beclin-1 pathway were measured. Sitagliptin attenuated injuries of endothelium in vivo and in vitro. The expression of microtubuleassociated protein 1 light chain 3 II (LC3II) and beclin-1 were increased in aortas of diabetic rats and cells cultured with high-glucose, while sitagliptin inhibited the over-expression of LC3II and beclin-1. In vitro pre-treatment with sitagliptin decreased rapamycin-induced autophagy. However, after pretreatment with rapamycin, the protective effect of sitagliptin on endothelial cells was abolished. Further studies revealed sitagliptin increased the expression of Bcl-2, while inhibited the expression of JNK in vivo. Sitagliptin attenuates injuries of vascular endothelial cells caused by high glucose through inhibiting over-activated autophagy. JNK-Bcl-2-Beclin-1 pathway may be involved in this process.

(Poly)phenol-Rich Diets in the Management of Endothelial Dysfunction in Diabetes Mellitus: Biological Properties in Cultured Endothelial Cells.

Processed and ready-to-eat foods become routinely consumed resulting in a sharp rise of sugar intake in people's daily diets. The inclusion of fresh fruits and vegetables rich in (poly)phenols has been encouraged by the World Health Organization (WHO) as part of the daily choices to ameliorate endothelial dysfunction and ease the socio-economic burden of diabetes. Research in Food, Nutrition, and Cell Metabolism areas is revealing that the health benefits of (poly)phenol-rich foods go beyond their antioxidant properties and are in fact key modulators of redox and glycaemia status, and inflammatory response contributing to improved endothelial function and vascular health in diabetes. Other beneficial aspects include appetite modulation, regulation of hydrolytic enzymes involved in sugar and lipid metabolism, and mediation of cell-cell aggregation events. This work overviews the current knowledge on the biological properties of ingested (poly)phenols in cultured endothelial cells with emphasis on the circulating (poly)phenols, providing support to (poly)phenol-rich diets as alternatives to drug-based therapies in the prevention, treatment, and management of diabetes. A critical evaluation on the caveats and challenges involve in current experimental cell-based designs and approaches adopted is also discussed.

The role of diabetes in the onset and development of endothelial dysfunction

The vascular endothelium performs many functions. It is a key regulator of vascular homeostasis, maintains a balance between vasodilation and vasoconstriction, inhibition and stimulation of smooth muscle cell migration and proliferation, fibrinolysis and thrombosis, and is involved to regulation of platelet adhesion and aggregation. Endothelial dysfunction (ED) plays the critical role in pathogenesis of diabetes mellitus (DM) vascular complications. The purpose of this review was to consider the mechanisms leading to the occurrence of ED in DM. The paper discusses current literature data concerning the role of hyperglycemia, oxidative stress, advanced glycation end products in endothelial alteration. A separate section is devoted to the particularities of the functioning of the antioxidant system and their significance in the development of ED in DM. The analysis of the literature allows to conclude that pathological activation of glucose utilization pathways causes damage of endothelial cells, which is accompanied by disorders of all their basic functions. Metabolic disorders in DM cause a pronounced imbalance of free radical processes and antioxidant defense, accompanied by oxidative stress of endotheliocytes, which contributes to the progression of ED and the development of vascular complications. Many aspects of multicomponent regulatory reactions in the pathogenesis of the development of ED in DM have not been sufficiently studied.

Acetylcholine iontophoresis in diabetic patients with and without peripheral neuropathy: a potential therapeutic tool

BackgroundIontophoresis had been widely used as a therapeutic option in the field of dermatology and physiotherapy. In vascular medicine, vasodilating response to acetylcholine (ACh) iontophoresis had been also previously studied in the evaluation of endothelial dysfunction in diabetes mellitus and its microvascular complications but less was published about its therapeutic implementations. The current study aimed at investigating the therapeutic role of ACh iontophoresis in the improvement of endothelial dysfunction seen in diabetic patients with and without peripheral neuropathy (PN).Patients and methodsForty patients with type 2 diabetes mellitus, 20 with and 20 without PN, were subjected to a therapeutic program of ACh iontophoresis three times a week for 2 successive weeks ‘long-term iontophoresis’. Percentage change in perfusion was measured in the two groups using laser Doppler flowmetry. Readings were taken pretreatment and post-treatment on three occasions: at baseline temperature, after local warming to 35°C, and at maximal flow after exposure to ACh iontophoresis ‘short-term iontophoresis’.ResultsPerfusion significantly improved after 2 weeks of therapy in the two groups with percentage change improvement of 180.65 vs. 131.50% in the baseline, 219.45 vs. 149.40% after local warming to 35°C and 269.60 vs. 236.95% after short-term ACh iontophoresis in patients without and those with PN, respectively, with P values of 0.0004, 0.0005, and 0.049, respectively.ConclusionACh iontophoresis may be an optional treatment procedure for improving cutaneous perfusion in diabetics for further randomized control studies.

Functional blocking of Ninjurin1 as a strategy for protecting endothelial cells in diabetes mellitus.

Ongoing efforts to remove pathological inflammatory stimuli are crucial for the protection of endothelial cells in diabetes. Nerve injury-induced protein 1 (Ninj1) is an adhesion molecule that not only contributes to inflammation but also regulates the apoptosis of endothelial cells. In the present study, Ninj1 was found highly expressed in endothelial cells in Type 2 diabetic mice and increased in high-glucose (HG) cultured HUVECs. Furthermore, we found that Ninj1 levels are up-regulated in endothelial cells in clinical specimens of diabetic patients when compared with nondiabetic tissues, indicating a biological correlation between Ninj1 and endothelial pathophysiology in diabetic condition. Functional blocking of Ninj1 promoted endothelial tube formation and eNOS phosphorylation in the HG condition. Additionally, blocking Ninj1 inhibited the activation of caspase-3 and increased the Bcl-2/Bax ratio, thus inhibiting HUVECs apoptosis induced by HG. HG-induced ROS overproduction, p38 MAPK and NF-κB activation, and the overexpression of VCAM-1, ICAM-1, MCP-1, and IL-6 genes were ameliorated after Ninj1 was blocked. Using the signaling pathway inhibitor LY294002, we found that Bcl-2 expression and eNOS phosphorylation after Ninj1 blockade were regulated via PI3K/Akt signaling pathway. The in vivo endothelial contents, α-SMA+PECAM-1+ vascular numbers, and blood perfusion in the hindlimb were markedly up-regulated after Ninj1 was blocked. According to our findings, functional blocking of Ninj1 shows protective effects on diabetic endothelial cells both in vitro and in vivo Thus, we consider Ninj1 to be a potential therapeutic target for preventing endothelial dysfunction in diabetes mellitus.

Rhodiola crenulata Attenuates High Glucose Induced Endothelial Dysfunction in Human Umbilical Vein Endothelial Cells.

Rhodiola crenulata root extract (RCE), a traditional Chinese medicine, has been shown to regulate glucose and lipid metabolism via the AMPK pathway in high glucose (HG) conditions. However, the effect of RCE on HG-induced endothelial dysfunction remains unclear. The present study was designed to examine the effects and mechanisms of RCE against hyperglycemic insult in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were pretreated with or without RCE and then exposed to 33[Formula: see text]mM HG medium. The cell viability, nitrite production, oxidative stress markers, and vasoactive factors, as well as the mechanisms underlying RCE action, were then investigated. We found that RCE significantly improved cell death, nitric oxide (NO) defects, and oxidative stress in HG conditions. In addition, RCE significantly decreased the HG-induced vasoactive markers, including endothelin-1 (ET-1), fibronectin, and vascular endothelial growth factor (VEGF). However, the RCE-restored AMPK-Akt-eNOS-NO axis and cell viability were abolished by the presence of an AMPK inhibitor. These findings suggested that the protective effects of RCE were associated with the AMPK-Akt-eNOS-NO signaling pathway. In conclusion, we showed that RCE protected endothelial cells from hyperglycemic insult and demonstrated its potential for use as a treatment for endothelial dysfunction in diabetes mellitus.

Restoration of autophagy in endothelial cells from patients with diabetes mellitus improves nitric oxide signaling

BackgroundEndothelial dysfunction contributes to cardiovascular disease in diabetes mellitus. Autophagy is a multistep mechanism for the removal of damaged proteins and organelles from the cell. Under diabetic conditions, inadequate autophagy promotes cellular dysfunction and insulin resistance in non-vascular tissue. We hypothesized that impaired autophagy contributes to endothelial dysfunction in diabetes mellitus. Methods and resultsWe measured autophagy markers and endothelial nitric oxide synthase (eNOS) activation in freshly isolated endothelial cells from diabetic subjects (n = 45) and non-diabetic controls (n = 41). p62 levels were higher in cells from diabetics (34.2 ± 3.6 vs. 20.0 ± 1.6, P = 0.001), indicating reduced autophagic flux. Bafilomycin inhibited insulin-induced activation of eNOS (64.7 ± 22% to −47.8 ± 8%, P = 0.04) in cells from controls, confirming that intact autophagy is necessary for eNOS signaling. In endothelial cells from diabetics, activation of autophagy with spermidine restored eNOS activation, suggesting that impaired autophagy contributes to endothelial dysfunction (P = 0.01). Indicators of autophagy initiation including the number of LC3-bound puncta and beclin 1 expression were similar in diabetics and controls, whereas an autophagy terminal phase indicator, the lysosomal protein Lamp2a, was higher in diabetics. In endothelial cells under diabetic conditions, the beneficial effect of spermidine on eNOS activation was blocked by autophagy inhibitors bafilomycin or 3-methyladenine. Blocking the terminal stage of autophagy with bafilomycin increased p62 (P = 0.01) in cells from diabetics to a lesser extent than in cells from controls (P = 0.04), suggesting ongoing, but inadequate autophagic clearance. ConclusionInadequate autophagy contributes to endothelial dysfunction in patients with diabetes and may be a target for therapy of diabetic vascular disease.

Bone Morphogenic Protein 4-Smad-Induced Upregulation of Platelet-Derived Growth Factor AA Impairs Endothelial Function.

Bone morphogenic protein 4 (BMP4) is an important mediator of endothelial dysfunction in cardio-metabolic diseases, whereas platelet-derived growth factors (PDGFs) are major angiogenic and proinflammatory mediator, although the functional link between these 2 factors is unknown. The present study investigated whether PDGF mediates BMP4-induced endothelial dysfunction in diabetes mellitus. We generated Ad-Bmp4 to overexpress Bmp4 and Ad-Pdgfa-shRNA to knockdown Pdgfa in mice through tail intravenous injection. SMAD4-shRNA lentivirus, SMAD1-shRNA, and SMAD5 shRNA adenovirus were used for knockdown in human and mouse endothelial cells. We found that PDGF-AA impaired endothelium-dependent vasodilation in aortas and mesenteric resistance arteries. BMP4 upregulated PDGF-AA in human and mouse endothelial cells, which was abolished by BMP4 antagonist noggin or knockdown of SMAD1/5 or SMAD4. BMP4-impared relaxation in mouse aorta was also ameliorated by PDGF-AA neutralizing antibody. Tail injection of Ad-Pdgfa-shRNA ameliorates endothelial dysfunction induced by Bmp4 overexpression (Ad-Bmp4) in vivo. Serum PDGF-AA was elevated in both diabetic patients and diabetic db/db mice compared with nondiabetic controls. Pdgfa-shRNA or Bmp4-shRNA adenovirus reduced serum PDGF-AA concentration in db/db mice. PDGF-AA neutralizing antibody or tail injection with Pdgfa-shRNA adenovirus improved endothelial function in aortas and mesenteric resistance arteries from db/db mice. The effect of PDGF-AA on endothelial function in mouse aorta was also inhibited by Ad-Pdgfra-shRNA to inhibit PDGFRα. The present study provides novel evidences to show that PDGF-AA impairs endothelium-dependent vasodilation and PDGF-AA mediates BMP4-induced adverse effect on endothelial cell function through SMAD1/5- and SMAD4-dependent mechanisms. Inhibition of PGDF-AA ameliorates vascular dysfunction in diabetic mice.

In Vivo Effects of Quercetin in Association with Moderate Exercise Training in Improving Streptozotocin-Induced Aortic Tissue Injuries.

Background: Diabetes mellitus (DM) is a chronic endocrine-metabolic disorder associated with endothelial dysfunction. Hyperglycemia, dyslipidemia and abnormal nitric oxide-mediated vasodilatation are the major causal factors in the development of endothelial dysfunction in DM. The prevention of endothelial dysfunction may be a first target against the appearance of atherosclerosis and cardiovascular diseases. We have investigated the synergistic protective effects of quercetin administration and moderate exercise training on thoracic aorta injuries induced by diabetes. Methods: Diabetic rats that performed exercise training were subjected to a swimming training program (1 h/day, 5 days/week, 4 weeks). The diabetic rats received quercetin (30 mg/kg body weight/day) for 4 weeks. At the end of the study, the thoracic aorta was isolated and divided into two parts; one part was immersed in 10% formalin for histopathological evaluations and the other was frozen for the assessment of oxidative stress markers (malondialdehyde, MDA and protein carbonyls groups, PC), the activity of antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT), nitrite plus nitrate (NOx) production and inducible nitric oxide synthase (iNOS) protein expression. Results: Diabetic rats showed significantly increased MDA and PC levels, NOx production and iNOS expression and a reduction of SOD and CAT activity in aortic tissues. A decrease in the levels of oxidative stress markers, NOx production and iNOS expression associated with elevated activity of antioxidant enzymes in the aortic tissue were observed in quercetin-treated diabetic trained rats. Conclusions: These findings suggest that quercetin administration in association with moderate exercise training reduces vascular complications and tissue injuries induced by diabetes in rat aorta by decreasing oxidative stress and restoring NO bioavailability.

Abstract 18064: Effect of Fluctuations in Glucose Levels on Vascular Endothelial Dysfunction and Clinical Outcomes in Coronary Artery Disease (CAD) Patients Without Diabetes Mellitus (DM)

Background: Fluctuations in glucose levels give rise to inflammation and endothelial dysfunction by increasing oxidative stress. Mean amplitude of glycemic excursions (MAGE) is commonly used as a degree of fluctuations in glucose level, and play a significant role in vascular endothelial dysfunction in diabetes mellitus (DM) patients, but not so clear in non-DM patients. Vascular endothelial dysfunction is associated with an increased risk of cardiovascular events. Thus, we examined the impact of MAGE on vascular endothelial dysfunction and clinical outcomes in non-DM patients with CAD. Methods: We analyzed 48 CAD patients following percutaneous coronary intervention (PCI) during 12 months, and assessed the relation among MAGE measured by continuous glucose monitoring (CGM), the level of high-sensitivity CRP (hs-CRP), and reactive hyperemia index (RHI) measured from RH-PAT (reactive hyperemia peripheral arterial tonometry). Cardiovascular events were cardiovascular death, myocardial infarction, unstable angina, and revascularization. Results: In clinical characteristics, HbA1c and MAGE were 5.96±0.40% and 62.5±32.6mg/dl. MAGE correlated with hs-CRP (r=0.426; P=0.003) and RHI (r=–0.403; P=0.007), but not correlated with body mass index (BMI), HbA1c, LDL cholesterol, and systolic blood pressures. In short, high glycemic excursions (high MAGE) is associated with high inflammation (high level of hs-CRP) and vascular endothelial dysfunction (low RHI). When patients were classified into MAGE&lt;65mg/dl (normal glycemic excursions) and MAGE&gt;65mg/dl (high glycemic excursions), group of MAGE&gt;65mg/dl showed significant higher hs-CRP (0.05±0.03 vs 0.15±0.15mg/dl, P&lt;0.001) and lower RHI (1.98±0.45 vs 1.74±0.38, P=0.003) compared with group of MAGE&lt;65mg/dl. Multivariate analysis for clinical outcomes identified high MAGE as predictive factors (OR4.7, P=0.032). In ROC curve, MAGE is predictive index for cardiovascular events (AUC 0.533, P=0.01). Conclusions: Fluctuations in glucose levels are associated with inflammation, endothelial dysfunction, and cardiovascular events. And, MAGE may be good predictive index for cardiovascular events in CAD patients without DM.

Abstract 10874: O-Linked β-N-acetylglucosamine Modification is Increased in Freshly Isolated Human Endothelial Cells in Type 2 Diabetes

Background: Diabetes mellitus (DM) is characterized by hyperglycemia that may contribute to abnormal vascular function. High glucose levels upregulate the hexosamine biosynthesis pathway leading to protein glycosylation with O-linked N-acetylglucosamine (O-GlcNAc). We sought to investigate the functional relevance of O-GlcNAc modification to endothelial dysfunction in DM. Method and Results: Freshly isolated endothelial cells obtained by J-wire biopsy from patients with DM had impaired insulin-mediated eNOS phosphorylation at Ser1177 compared to controls. Incubation in normal glucose conditions (5mM, 24hours) restored insulin-mediated eNOS phosphorylation in endothelial cells from patients with DM whereas insulin resistance persisted in high glucose conditions (30mM), suggesting a link between glucose levels and endothelial insulin resistance. Endothelial O-GlcNAc level was higher in diabetes patients compared to healthy controls (22±8 vs 12±5%, N=18/10, P=0.003, Figure A). Higher endothelial O-GlcNAc levels correlated with higher body mass index (P= 0.03), fasting blood glucose (P=0.01), HbA1C (P=0.02), and triglycerides (P=0.01). Normal glucose conditions lowered O-GlcNAc levels in endothelial cells isolated from patients with DM (P=0.028, Figure B). Ongoing studies are evaluating the effect of agents that reducing O-GlcNAc on insulin-mediated eNOS phosphorylation. Conclusion: Our results provide evidence that O-GlcNAc is more abundant in the endothelium of diabetic patients and glucose normalization reduces O-GlcNAc and improves reaction to insulin. Further work is needed to determine the contribution of O-GlcNAc modification to vascular disease in diabetes.

Tissue-specific up-regulation of arginase I and II induced by p38 MAPK mediates endothelial dysfunction in type 1 diabetes mellitus.

Emerging evidence suggests a selective up-regulation of arginase I in diabetes causing coronary artery disease; however, the mechanisms behind this up-regulation are still unknown. Activated p38 MAPK has been reported to increase arginase II in various cardiovascular diseases. We therefore tested the role of p38 MAPK in the regulation of arginase I and II expression and its effect on endothelial dysfunction in diabetes mellitus. Endothelial function was determined in septal coronary (SCA), left anterior descending coronary (LAD) and mesenteric (MA) arteries from healthy and streptozotocin-induced diabetic Wistar rats by wire myographs. Arginase activity and protein levels of arginase I, II, phospho-p38 MAPK and phospho-endothelial NOS (eNOS) (Ser(1177) ) were determined in these arteries from diabetic and healthy rats treated with a p38 MAPK inhibitor in vivo. Diabetic SCA and MA displayed impaired endothelium-dependent relaxation, which was prevented by arginase and p38 MAPK inhibition while LAD relaxation was not affected. Arginase I, phospho-p38 MAPK and eNOS protein expression was increased in diabetic coronary arteries. In diabetic MA, however, increased expression of arginase II and phospho-p38 MAPK, increased arginase activity and decreased expression of eNOS were observed. All these effects were reversed by p38 MAPK inhibition. Diabetes-induced activation of p38 MAPK causes endothelial dysfunction via selective up-regulation of arginase I expression in coronary arteries and arginase II expression in MA. Therefore, regional differences appear to exist in the arginase isoforms contributing to endothelial dysfunction in type 1 diabetes mellitus.

Monoamine oxidases are novel sources of cardiovascular oxidative stress in experimental diabetes.

Diabetes mellitus (DM) is widely recognized as the most severe metabolic disease associated with increased cardiovascular morbidity and mortality. The generation of reactive oxygen species (ROS) is a major event causally linked to the development of cardiovascular complications throughout the evolution of DM. Recently, monoamine oxidases (MAOs) at the outer mitochondrial membrane, with 2 isoforms, MAO-A and MAO-B, have emerged as novel sources of constant hydrogen peroxide (H2O2) production in the cardiovascular system via the oxidative deamination of biogenic amines and neurotransmitters. Whether MAOs are mediators of endothelial dysfunction in DM is unknown, and so we studied this in a streptozotocin-induced rat model of diabetes. MAO expression (mRNA and protein) was increased in both arterial samples and hearts isolated from the diabetic animals. Also, H2O2 production (ferrous oxidation - xylenol orange assay) in aortic samples was significantly increased, together with an impairment of endothelium-dependent relaxation (organ-bath studies). MAO inhibitors (clorgyline and selegiline) attenuated ROS production by 50% and partially normalized the endothelium-dependent relaxation in diseased vessels. In conclusion, MAOs, in particular the MAO-B isoform, are induced in aortas and hearts in the streptozotocin-induced diabetic rat model and contribute, via the generation of H2O2, to the endothelial dysfunction associated with experimental diabetes.