Vascular Damage In Diabetes Research Articles

Mineralocorticoid receptor blockade prevents vascular remodelling in a rodent model of type 2 diabetes mellitus

Mineralocorticoid receptors (MRs), which are activated by mineralocorticoids and glucocorticoids, actively participate in mechanisms that affect the structure and function of blood vessels. Although experimental and clinical evidence shows that vascular damage in diabetes is associated with structural alterations in large and small arteries, the role of MR in this process needs further studies. Thus, we tested the hypothesis that MR, through redox-sensitive mechanisms, plays a role in diabetes-associated vascular remodelling. Male, 12-14-weeks-old db/db mice, a model of type2 diabetes and their non-diabetic counterpart controls (db/+) were treated with spironolactone (MR antagonist, 50mg/kg/day) or vehicle for 6weeks. Spironolactone treatment did not affect blood pressure, fasting glucose levels or weight gain, but increased serum potassium and total cholesterol in both, diabetic and control mice. In addition, spironolactone significantly reduced serum insulin levels, but not aldosterone levels in diabetic mice. Insulin sensitivity, evaluated by the HOMA (homoeostatic model assessment)-index, was improved in spironolactone-treated diabetic mice. Mesenteric resistance arteries from vehicle-treated db/db mice exhibited inward hypertrophic remodelling, increased number of smooth muscle cells and increased vascular stiffness. These structural changes, determined by morphometric analysis and with a myography for pressurized arteries, were prevented by spironolactone treatment. Arteries from vehicle-treated db/db mice also exhibited augmented collagen content, determined by Picrosirius Red staining and Western blotting, increased reactive oxygen species (ROS) generation, determined by dihydroethidium (DHE) fluorescence, as well as increased expression of NAD(P)H oxidases 1 and 4 and increased activity of mitogen-activated protein kinases (MAPKs). Spironolactone treatment prevented all these changes, indicating that MR importantly contributes to diabetes-associated vascular dysfunction by inducing oxidative stress and by increasing the activity of redox-sensitive proteins.

Abstract 512: RAGE-dependent Down-regulation of Glyoxalase-1 Impairs Inflammatory Response and Angiogenesis in Hind Limb Ischemia in Diabetic Mice

Critical limb ischemia is a serious form of peripheral artery disease. Previous studies linked the advanced glycation end products (AGEs) and its receptor, RAGE, to impairment of angiogenesis in hind limb ischemia in diabetes. Here, we tested the hypothesis that reduction of RAGE ligand, AGEs, by transgenic (Tg) overexpression of glyoxalase-1 (Glo1), an enzyme that detoxifies AGE precursor methylglyoxal, improves inflammatory responses, angiogenesis and blood flow recovery in hind limb ischemia in diabetic mice. Wild type (WT), Ager-/- (devoid of RAGE) and Tg (Glo1) mice were rendered diabetic (D) with streptozotocin (stz); non-diabetic (ND) cohorts were treated with buffer alone. After two month of diabetes, at age 16 weeks, mice were subjected to unilateral hind limb ischemia. In skeletal muscle tissue within the tributary of the femoral arterial system, a significant increase of Glo1 mRNA was evident in both ND and D Ager-/- mice vs. WT mice after ischemia (p<0.05). A significant reduction in carboxymethyl lysine (CML)-AGEs modified protein was observed in Tg (Glo1) mice compared to WT mice at baseline and on day 5 after ischemia in non-diabetes and diabetes (p<0.05). A significant increase of inflammatory mediators, early growth response-1 (Egr1) (p<0.001) and monocyte chemotactic protein-1 (MCP-1/CCL2) (p<0.01) was observed in ND and D Tg (Glo1) vs. WT mice after ischemia. In parallel, significantly augmented inflammatory cell infiltration identified by increasing CD68+ cell numbers in skeletal muscle tissues was observed in ND and D Tg (Glo1) compared to WT on day 7 after ischemia (p<0.05). Tg(Glo1) mice displayed significantly improved capillary density in both the non-diabetic and diabetic states compared to WT mice on day 28 after ischemia (p<0.05 and p<0.01). Increased blood flow was observed in ND and D Tg (Glo1) mice vs. WT controls (p<0.01). Our findings reveal that RAGE-dependent down-regulation of Glo1 is mechanistically linked, at least in part, to the impaired angiogenic responses observed in WT diabetic mice after hind limb ischemia, suggesting that suppression of AGE-RAGE axis and consequent upregulation of the Glo1 pathway may provide an important therapeutic target in the prevention of diabetic vascular damage.

Vascular injury in diabetic db/db mice is ameliorated by atorvastatin: role of Rac1/2-sensitive Nox-dependent pathways.

Oxidative stress [increased bioavailability of reactive oxygen species (ROS)] plays a role in the endothelial dysfunction and vascular inflammation, which underlie vascular damage in diabetes. Statins are cholesterol-lowering drugs that are vasoprotective in diabetes through unknown mechanisms. We tested the hypothesis that atorvastatin decreases NADPH oxidase (Nox)-derived ROS generation and associated vascular injury in diabetes. Lepr(db)/Lepr(db) (db/db) mice, a model of Type 2 diabetes and control Lepr(db)/Lepr(+) (db/+) mice were administered atorvastatin (10 mg/kg per day, 2 weeks). Atorvastatin improved glucose tolerance in db/db mice. Systemic and vascular oxidative stress in db/db mice, characterized by increased plasma TBARS (thiobarbituric acid-reactive substances) levels and exaggerated vascular Nox-derived ROS generation respectively, were inhibited by atorvastatin. Cytosol-to-membrane translocation of the Nox regulatory subunit p47(phox) and the small GTPase Rac1/2 was increased in vessels from db/db mice compared with db/+ mice, an effect blunted by atorvastatin. The increase in vascular Nox1/2/4 expression and increased phosphorylation of redox-sensitive mitogen-activated protein kinases (MAPKs) was abrogated by atorvastatin in db/db mice. Pro-inflammatory signalling (decreased IκB-α and increased NF-κB p50 expression, increased NF-κB p65 phosphorylation) and associated vascular inflammation [vascular cell adhesion molecule-1 (VCAM-1) expression and vascular monocyte adhesion], which were increased in aortas of db/db mice, were blunted by atorvastatin. Impaired acetylcholine (Ach)- and insulin (INS)-induced vasorelaxation in db/db mice was normalized by atorvastatin. Our results demonstrate that, in diabetic mice, atorvastatin decreases vascular oxidative stress and inflammation and ameliorates vascular injury through processes involving decreased activation of Rac1/2 and Nox. These findings elucidate redox-sensitive and Rac1/2-dependent mechanisms whereby statins protect against vascular injury in diabetes.

Physicochemical analysis of structural alteration and advanced glycation end products generation during glycation of H2A histone by 3-deoxyglucosone.

Advanced glycation end-products comprise a complex and heterogeneous group of compounds that have been implicated in diabetes-related complications. The importance of the Maillard reaction is depicted by the formation of reactive intermediate products known as α-oxoaldehydes, such as 3-deoxyglucosone (3-DG). This product has been found to be involved in accelerated vascular damage in diabetes. In the present study, calf thymus histone H2A was reacted with 3-DG, and the generation of advanced glycation end products was investigated by determining the degree of side chain modifications (lysine and arginine residues), Amadori products, carbonyl content, N(ε) -carboxymethyl lysine, and pentosidine using various physicochemical techniques. Moreover, fluorescence, absorbance as well as structural characteristics of glycated-H2A were comprehensively investigated. Overall, this study demonstrates structural perturbation, formation of different intermediates, and AGEs that are believed to hamper the normal functioning of H2A histone, compromising the integrity of chromatin structures and function in secondary complications of diabetes.

Treatment of painful diabetic neuropathy.

Painful diabetic neuropathy (PDN) is a debilitating consequence of diabetes that may be present in as many as one in five patients with diabetes. The objective assessment of PDN is difficult, making it challenging to diagnose and assess in both clinical practice and clinical trials. No single treatment exists to prevent or reverse neuropathic changes or to provide total pain relief. Treatment of PDN is based on three major approaches: intensive glycaemic control and risk factor management, treatments based on pathogenetic mechanisms, and symptomatic pain management. Clinical guidelines recommend pain relief in PDN through the use of antidepressants such as amitriptyline and duloxetine, the γ-aminobutyric acid analogues gabapentin and pregabalin, opioids and topical agents such as capsaicin. Of these medications, duloxetine and pregabalin were approved by the US Food and Drug Administration (FDA) in 2004 and tapentadol extended release was approved in 2012 for the treatment of PDN. Proposed pathogenetic treatments include α-lipoic acid (stems reactive oxygen species formation), benfotiamine (prevents vascular damage in diabetes) and aldose-reductase inhibitors (reduces flux through the polyol pathway). There is a growing need for studies to evaluate the most potent drugs or combinations for the management of PDN to maximize pain relief and improve quality of life. A number of agents are potential candidates for future use in PDN therapy, including Nav 1.7 antagonists, N-type calcium channel blockers, NGF antibodies and angiotensin II type 2 receptor antagonists.

Vascular Adhesion Protein-1 Is Significantly Elevated in Heart Transplant Recipients and Chronic Heart Failure Patients With Comorbidities.

Background: VAP-1 (vascular adhesion protein-1) is a copper-containing SSAO (semi-carbazide sensitive amine oxidase) secreted by vascular smooth muscle cells, adipocytes, and endothelial cells with functional monoamine oxidase activity. The oxidation process generates harmful products that may be involved in causing atherosclerosis and vascular damage in diabetes. Elevation of SSAO activity is observed in atherosclerosis, diabetes mellitus and obesity. Taking all these data into consideration, the aim of the study was to assess VAP-1 levels and its correlations with endothelial injury markers in prevalent heart allograft recipients (n=128) and patients with chronic heart failure (n=78). Methods:Complete blood count, urea, serum lipids, fasting glucose, creatinine, were studied by standard laboratory method in the hospital central laboratory. We assessed markers of endothelial function/injury and inflammation: vWF (von Willebrand factor), TWEAK, C-Reactive Protein with commercially available assays. Results: The mean serum VAP-1 in was lower than in patients with chronic heart failure. In patients with chronic heart failure VAP-1 was related to age (0.31,p<0.01), ejection fraction-EF (r=0.23, p<0.05), presence of hypertension (r=0.28, p<0.01), presence of diabetes (r=0.31,p<0.01), TWEAK (r=0.21, p<0.05). In heart transplant recipients VAP-1 correlated with estimated glomerular filtration rate-eGFR (r=-0.19, p<0.05), age (r=0.17, p<0.05), presence of diabetes (r=0.29, p<0.01), EF (r=-0.34, p<0.01), presence of hypertension (r=0.22, p<0.05), TWEAK (r=0.17, p<0.05), NYHA class (0.33, p<0.001). In both groups of the studied patients VAP-1 was significantly higher in patients with diabetes, hypertension, and eGFR< 60 ml/min when compared to patients without diabetes, with normotension and eGFR> 60 ml/min.(all p<0.01). Concluding, VAP-1, elevated predominantly in patients with comorbidities such as diabetes, hypertension chronic kidney disease may contribute to the worse outcomes in both of the population studied. It may also contribute to the progression of atherosclerosis with its complications.

Cardiovascular Manifestations of Hyperglycemia: A Review Article

The overbearing financial burden imposed by the U.S. healthcare system is a complex problem which must be addressed soon. Diabetes, with its multiple cardiovascular sequelae, is currently one of the largest contributors and threatens to worsen as the obesity epidemic blossoms. The implications of atherosclerosis and hypertension related to diabetes may take years to become evident, making the overall disease process a particularly insidious one. Similarities between the biochemical mechanisms of vascular damage in diabetes may someday be the key to preventing its significant morbidity. Until we are able to capitalize on the similarities in the development of complications of hyperglycemia, preventative medicine should be the focus. Lessons should be learned from the widespread success of anti-tobacco legislation and educational programs in decreasing the prevalence of smoking and subsequent pulmonary disease. New York has already passed legislation limiting the size of sugary drinks that can be sold in the city. Efforts should be made to redirect care from the end stages of this particular disease to preventing it in the lower socioeconomic class, where poor diet may be more of an issue.

Stroke : Highlights of Selected Articles

HomeStrokeVol. 44, No. 8Stroke: Highlights of Selected Articles Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBStroke: Highlights of Selected Articles Originally published1 Aug 2013https://doi.org/10.1161/STROKEAHA.113.002626Stroke. 2013;44:2092Glycosylated Hemoglobin A1 Predicts Risk for Symptomatic Hemorrhage After Thrombolysis for Acute StrokeSymptomatic intracerebral hemorrhage after intravenous treatment with tissue-type plasminogen activator (tPA) in acute ischemic stroke is a potentially devastating event with a high mortality rate. Many factors are thought to increase the risk of hemorrhage, including damage to the microvasculature. Hemoglobin A1 (HbA1c) is a marker for long-term elevated glucose level and is used for monitoring diabetic vascular damage. In this retrospective analysis, Rocco et al investigated the predictive value of HbA1c for symptomatic intracerebral hemorrhage and clinical outcome in patients treated with intravenous tPA for acute ischemic stroke. The authors reviewed >1000 patients treated with tPA from 1998 to 2011 at the Neurological Department in Heidelberg, Germany. Any hemorrhage occurred in 222 patients (19.9%); 43 of those had symptomatic intracerebral hemorrhage (3.9%) per Safe Implementation of Treatments in Stroke definition and 95 (8.5%) per National Institute of Neurological Disorders and Stroke definition. In multivariate analysis, HbA1c was highly significantly associated with any hemorrhage and symptomatic intracerebral hemorrhage with a cut-off value of 6.5%, regardless of the definition used. By contrast, blood glucose at baseline was not statistically significantly associated with any type of hemorrhage. In multivariate analysis, age, National Institutes of Health Stroke Scale score on admission, and HbA1c were predictors of dependent outcome (modified Rankin Scale, 3–5). HbA1c is an important predictor of symptomatic intracerebral hemorrhage after thrombolysis for acute ischemic stroke. These results suggest that hemorrhage after thrombolysis may be a consequence of long-term vascular injury rather than of acute hyperglycemia. Patients should not be excluded from intravenous tPA with elevated HbA1c. However, if validated in larger prospective studies, these patients may warrant more intensive monitoring following tPA. See p 2134.Size Ratio Can Highly Predict Rupture Risk in Intracranial Small (<5 mm) AneurysmsThe decision-making process in the management of unruptured cerebral aneurysms is controversial. The risk of rupture increases with increasing aneurysm size. There are, however, a significant number of cases of subarachnoid hemorrhage from ruptured aneurysms <5 mm. Most studies use aneurysm diameter as a clinical variable when assessing risk of rupture. This study aimed to identify other parameters that highly predict the rupture risk of small (<5 mm) unruptured cerebral aneurysms. They reviewed a prospective cohort of 854 aneurysmal subarachnoid hemorrhage patients from 2003 and 2011 in Sapporo City, Japan. The size, aneurysm-to-vessel size ratio, and distribution were precisely compared between the ruptured and unruptured aneurysms. The size ratio was defined as the ratio of the maximum aneurysm diameter to the average vessel diameter. The most frequent site of ruptured aneurysm was at the anterior communicating artery, and the most frequent site of unruptured aneurysm was the middle cerebral artery. The maximal diameter and the size ratio were significantly higher in the ruptured group than unruptured. In multivariate analysis, both size and size ratio were correlated with aneurysm rupture. Specifically regarding the small aneurysms, 27% of the ruptured cerebral aneurysms were <5 mm. In multivariate analysis, only size ratio was associated with rupture in the small aneurysm group. These results should be validated in further, large prospective registries. However, based on these results, the calculation of size ratio may represent a good marker of rupture risk in small aneurysms. See p 2169.Systemic Inflammatory Response Syndrome in Tissue-Type Plasminogen Activator–Treated Patients is Associated With Worse Short-term Functional OutcomeSystemic inflammatory response (SIRS) is a generalized inflammatory state. Previous research has shown that patients with severe acute ischemic stroke have increased risk of having SIRS. In the current study, the investigators looked at the differences in outcomes in SIRS and non-SIRS tissue-type plasminogen activator–treated patients. They retrospectively reviewed their stroke database from 2008 to 2011 for patients with SIRS, excluding patients with infection. Out of 241 tissue-type plasminogen activator–treated patients included in this study, 44 had evidence of SIRS (18.2%). Patients with SIRS were more likely to be black and had lower median total cholesterol at baseline. SIRS patients were more likely to have longer length of stay and greater odds of poor functional outcome. Adjusting for baseline National Institutes of Health Stroke Scale, age, and race, SIRS remained a predictor of poor functional outcome at discharge. SIRS was not a predictor of poor discharge disposition or in-hospital mortality. Larger prospective studies are needed to validate these results, which are limited due to the small sample size and retrospective nature. See p 2322. Previous Back to top Next FiguresReferencesRelatedDetails August 2013Vol 44, Issue 8 Advertisement Article InformationMetrics © 2013 American Heart Association, Inc.https://doi.org/10.1161/STROKEAHA.113.002626 Originally publishedAugust 1, 2013 PDF download Advertisement

A Key Role for ROCK in TNF-α–Mediated Diabetic Microvascular Damage

Leukocyte adhesion releases tumor necrosis factor (TNF)-α that contributes to endothelial damage in early diabetic retinopathy (DR). Rho/Rho-kinase (ROCK) signaling mediates retinal endothelial damage in early DR. However, whether ROCK regulates TNF-α-mediated diabetic vascular damage is unknown. Here, the contribution of ROCK to TNF-α-mediated microvascular damage is investigated. In DR patients and nondiabetic control subjects, the levels of membranous (m) TNF-α on neutrophils, soluble (s) TNF-α and its receptors in sera, were measured. In cultured microvascular endothelial cells, phosphorylation of myosin phosphatase target protein (MYPT)-1, a downstream target of ROCK, was investigated with TNF-α or DR sera pretreatment. TNF-α-induced intercellular adhesion molecule-1 (ICAM-1) and endothelial nitric oxide synthase (eNOS) phosphorylation were measured with and without ROCK inhibition by fasudil or ROCK-specific small-interfering RNA (siRNA). In isolated neutrophils from control subjects, MYPT-1 phosphorylation was investigated in the presence of TNF-α. The impact of ROCK inhibition by fasudil on TNF-α-induced integrin (CD18, CD11a, CD11b) and intracellular cytoskeletal changes were investigated. The serum levels of mTNF-α, sTNF-α, and its receptors were significantly elevated in DR patients. TNF-α as well as DR sera promoted MYPT-1 phosphorylation in endothelial cells, which was significantly reduced by anti-TNF-α neutralizing antibody. TNF-α-induced ICAM-1 expression, eNOS dephosphorylation, cytoskeletal changes, and CD11b/18 expression in neutrophils were significantly suppressed by fasudil as well as ROCK-specific siRNA. ROCK is a key mediator of TNF-α signaling in diabetic microvessels. The important role of TNF-α in early DR provides a new rationale for ROCK inhibition beyond the previously shown mechanisms.

Rosmarinic acid protects against experimental diabetes with cerebral ischemia: relation to inflammation response

BackgroundInflammatory activation plays a vital role in the pathophysiological mechanisms of stroke, exerting deleterious effects on the progression of tissue damage and may lead to the vascular damage in diabetes. The objectives of this study were to determine the effects of rosmarinic acid (RA) on a cultured neuronal cell line, SH-SY5Y in vitro and experimental ischemic diabetic stroke in vivo.MethodsFor oxygen-glucose deprivation (OGD) and tumor necrosis factor-α (TNF-α) stimulated SH-SY5Y cell line in vitro, SH-SY5Y cells were incubated with RA. For an in vivo experiment, diabetic rats were subjected to middle cerebral artery occlusion (MACO) for 40 minutes followed by reperfusion for 23 h.ResultsTreatment of SH-SY5Y cells with RA reduced the OGD-induced apoptosis and cytotoxicity, blocked TNF-α-induced nuclear transcription factor κB (NF-κB) activation, and decreased high-mobility group box1 (HMGB1) expression. At doses higher than 50 mg/kg, RA produced a significant neuroprotective potential in rats with ischemia and reperfusion (I/R). RA (50 mg/kg) demonstrated significant neuroprotective activity even after delayed administration at 1 h, 3 h and 5 h after I/R. RA 50 mg/kg attenuated histopathological damage, decreased brain edema, inhibited NF-κB activation and reduced HMGB1 expression.ConclusionThese data show that RA protects the brain against I/R injury with a favorable therapeutic time-window by alleviating diabetic cerebral I/R injury and attenuating blood–brain barrier (BBB) breakdown, and its protective effects may involve HMGB1 and the NF-κB signaling pathway.

Increased iNOS activity in vascular smooth muscle cells from diabetic rats: Potential role of Ca2+/calmodulin-dependent protein kinase II delta 2 (CaMKIIδ2)

ObjectiveInducible nitric oxide synthase (iNOS) expression may be increased by cytokine plasma levels contributing to vascular damage in diabetes. Besides transcriptional regulation, Ca2+/CaMKII may play a role in post-translationally controlled iNOS activity. We accordingly investigated the involvement of the Ca2+/CaMKIIδ2 signaling pathway in regulating lipopolysaccharide (LPS)-induced iNOS activity in cultured aortic vascular smooth muscle cells (VSMCs) from diabetic rats. Methods and resultsVSMCs obtained from 10 diabetic rats (DR) and 10 control rats (CR) were stimulated with 20 μg/ml LPS. After 24 h, iNOS protein levels were 1.37 fold increased in DR- vs CR-VSMCs (p < 0.05; Western Blot), while iNOS activity (conversion l-(3H)-arginine into l-(3H)-citrulline) and intracellular nitrotyrosine levels (immunofluorescence) were about 2.7 fold greater in DR- than in CR-VSMCs. Interestingly, LPS increased intracellular Ca2+ levels (Fluorescence video imaging) more markedly in DR- than in CR-VSMCs. This was associated with CaMKII activation by phosphorylation, a decreased amount of co-immunoprecipitating iNOS/CaMKIIδ2 (Western Blot) and increased iNOS activity. The CaMKII inhibitor KN-93 abolished all the LPS-effects. ConclusionThese results indicate that the Ca2+/CaMKIIδ2 signaling pathway may be an important regulator of iNOS activity in diabetes, and hence contribute to the potential development of innovative therapeutic strategies for vascular complications in diabetes.

VAP-1, a Novel Molecule Linked to Endothelial Damage and Kidney Function in Kidney Allograft Recipients

VAP-1 (vascular adhesion protein-1) is a copper-containing SSAO (semi-carbazide sensitive amine oxidase) secreted by vascular smooth muscle cells, adipocytes, and endothelial cells with functional monoamine oxidase activity. The oxidation process generates harmful products that may be involved in causing atherosclerosis and vascular damage in diabetes. Elevation of SSAO activity is observed in atherosclerosis, diabetes mellitus and obesity. On the other hand, renalase, with possible monoamine oxidase activity, which breaks down catecholamines like SSAO, is also expressed in the endothelium as well as in the kidney The aim of the study was to assess VAP-1 levels and its correlations with endothelial injury markers and renalase in 50 kidney allograft recipients. Methods: Complete blood count, urea, serum lipids, fasting glucose, creatinine, were studied by standard laboratory method in the hospital central laboratory. We assessed markers of endothelial function/injury: vWF (von Willebrand factor), thrombomodulin, ICAM (intracellular adhesion molecule), VCAM (vascular cell adhesion molecule), CD40L, CD44, CD146, inflammation: hsCRP, and IL-6 and adipocytokines: leptin, adiponectin, visfatin, apelin with commercially available assays. Results: The mean serum VAP-1 in Tx was significantly higher comparing to the control group. In kidney transplant recipients VAP-1 correlated with BMI (r=0.39, p< 0.01), CD44 (r=0.27, p< 0.05), hsCRP (r=0.28, p< 0.05), serum creatinine (r=0.29, p< 0.05), eGFR (CKD-EPI formula r=-0.27, p< 0.05, by MDRD r=-0.27, p< 0.05, by Cockcroft-Gault r=-0.35, p< 0.01), serum urea (r=0.27, p< 0.05), CD146 (r=0.49, p< 0.001), CD40L (r=0.26, p< 0.06), and renalase (r=0.34, p< 0.05)Figure: [VAP-1 and renalase in Ktx]In multiple regression analysis VAP-1 was predicted 80% by serum creatinine (beta value 0.33, p=0.01), and CD146 (beta value 43, p=0.0005) F=12.26, SE= 71.83 and p< 0.000001. Concluding, VAP-1, elevated in kidney transplant recipients, is predominantly dependent on endothelial damage and kidney function, which deteriorated with time after kidney transplantation and age.

The Role of microRNA-126 in Vascular Homeostasis

MicroRNAs are negative regulators of gene expression that have been shown to be essential elements in the coordination of complex regulatory pathways. One of these short non-coding RNAs, microRNA-126, is highly enriched in the vascular endothelium and was shown to play distinct roles in angiogenesis, vasculogenesis and endothelial inflammation. Abrogation of this microRNA leads to severe complications in the response in vascular development as well as vital repair mechanisms carried out by endothelial cells. Interestingly, recent data suggest that the homeostatic role of microRNA-126 may reach far beyond its endothelial functions as this microRNA was also found to be present in cells of the hematopoietic system and in microvesicles or 'free-form' in the periphery. MicroRNA-126 is controlling the fate and/or function of a variety of cells differentiating from the hematopoietic lineage, including megakaryocytes and erythrocytes. Recent studies identified circulating microRNA-126 as a biomarker for myocardial injury and vascular damage in diabetes. Furthermore, reports have suggested a protective role of circulating microRNA-126 in murine models of organ ischemia. Here, we review current insights in the role of microRNA-126 in vascular homeostasis and conclude that this microRNA may serve to integrate and facilitate both local as well as systemic functions in vascular maintenance and repair.

Glucose-dependent Insulinotropic Polypeptide (GIP) Inhibits Signaling Pathways of Advanced Glycation End Products (AGEs) in Endothelial Cells via its Antioxidative Properties

Glucose-dependent insulinotropic polypeptide (GIP) is one of the incretins, a gut hormone secreted from K cells in the intestine in response to food intake. It could be a potential therapeutic target for the treatment of patients with type 2 diabetes. However, effects of GIP on vascular injury remain unknown. Since interaction of advanced glycation end products (AGEs) with their receptor RAGE has been shown to play a crucial role in vascular damage in diabetes, this study investigated whether and how GIP blocked the deleterious effects of AGEs on human umbilical vein endothelial cells (HUVECs). GIP receptor was expressed in HUVECs. GIP, an analogue of cyclic AMP or inhibitors of NADPH oxidase inhibited the AGE-induced reactive oxygen species (ROS) generation in HUVECs. Furthermore, GIP reduced both RAGE mRNA and protein levels in HUVECs. GLP-1 also blocked the AGE-induced increase in mRNA levels of vascular cell adhesion molecule-1 (VCAM-1) and plasminogen activator inhibitor-1 in HUVECs. In addition, an antioxidant N-acetylcysteine mimicked the effects of GIP on RAGE and VCAM-1 gene expression in HUVECs. Our present study suggests that GIP could block the signal pathways of AGEs in HUVECs by reducing ROS generation and subsequent RAGE expression probably via GIP receptor-cyclic AMP axis.

Sitagliptin Augments Protective Effects of GLP-1 against Advanced Glycation End Product Receptor Axis in Endothelial Cells

Sitagliptin is a stable inhibitor of dipeptidyl peptidase-IV, a responsible enzyme that mainly inactivates glucagon-like peptide-1 (GLP-1), and now one of the widely used agents for the treatment of diabetes. However, effects of sitagliptin on vascular injury are largely unknown. Since advanced glycation end products (AGEs) and their receptor (RAGE) axis contribute to vascular damage in diabetes, we investigated here whether sitagliptin inhibits the AGE-RAGE-induced endothelial cell damage in vitro. Although effects of 10 pM GLP-1 or 0.5 μM sitagliptin monotherapy on RAGE gene and protein expression were modest, combination therapy completely blocked the AGE-induced increase in RAGE mRNA and protein levels in human umbilical vein endothelial cells (HUVEC). AGEs induced reactive oxygen species (ROS) generation and reduced endothelial nitric oxide synthase (eNOS) mRNA level in HUVEC, both of which were also completely blocked by the treatment with 10 pM GLP-1 and 0.5 μM sitagliptin, but not with GLP-1 or sitagliptin monotherapy. Further, anti-RAGE antibody restored the decrease in eNOS mRNA level in AGE-exposed HUVEC. The present study suggests that sitagliptin augments the effects of GLP-1 on eNOS mRNA level in AGE-exposed HUVEC by suppressing RAGE expression and subsequent ROS generation. Sitagliptin may work as a vasoprotecitve agent in diabetes by blocking the AGE-RAGE axis.

Innate immunity, through late complement components activation, contributes to the development of early vascular inflammation and morphologic alterations in experimental diabetes

ObjectiveTo verify if innate immunity, and namely the assembly of terminal complement complex (TCC) could be involved in the development of early diabetic vascular damage. Methods and resultsAt first in 2 groups of diabetic or non-diabetic Wistar rats the occurrence of basal or stimulated stable adherence to the endothelial layer and extravasation of circulating fluorescently-labelled leukocytes was assessed by using an in vivo videomicroscopy technique. In a second part of the study, the development of vascular damage in short term diabetes was studied in the genetically C6 deficient rats of the PVG strain, and compared with those observed in the wild-type C6 sufficient animals. Here, the analysis of mesentery vascular expression of mRNA for vascular cell adhesion molecule (VCAM)-1, transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), and platelet-derived growth factor (PDGF), the evaluation of intravascular protein levels of VCAM-1, TGF-β, CTGF, proliferative cell nuclear antigen (PCNA), as well as the assessment of structural changes and Complement components deposition at the mesentery arterial vascular wall were also performed. ConclusionsLeukocyte trafficking, mesentery arteries hypertrophy, extracellular matrix deposition, local vascular gene and protein expression of VCAM-1, TGF-β, CTGF and PCNA, as well as PGDF gene expression were all increased by short term diabetes, but all significantly reduced in the C6 deficient diabetic animals, thus suggesting an active role for TCC in the development of vascular inflammation in the early phases of experimental diabetes.

Short-term hyperglycemia increases arterial superoxide production and iron dysregulation in atherosclerotic monkeys

The incidence and severity of atherosclerotic vascular disease are increased in diabetic patients, in part because of increased production of reactive oxygen species (ROS). Previously, we found both increased atherosclerosis and arterial protein oxidation 6 months after streptozotocin-induced diabetes in monkeys fed an atherogenic diet, the pattern of which was indicative of redox-active transition metal involvement. The goal of this study was to determine if short-term (1 month) hyperglycemia increases oxidative stress and dysregulates iron metabolism before differences in atherosclerosis. Cynomolgus monkeys with preexisting atherosclerosis were stratified by dietary history and plasma lipids and received either streptozotocin (STZ-DM; n = 10) or vehicle (control; n = 10). One month after diabetes induction, blood and artery samples were collected. There were no differences in plasma lipoprotein cholesterol, arterial cholesterol, and atherosclerosis between control and STZ-DM. However, plasma lipid peroxides were elevated 137% (P < .01); arterial superoxide was increased 47% (P < .05); plasma ferritin, an indicator of whole-body iron stores, was 46% higher (P < .05); and iron deposition within aortic atherosclerotic lesions was more prevalent in STZ-DM compared with controls. Arterial levels of the antioxidant enzymes, superoxide dismutase, catalase, and heme oxygenase-1 were not higher in STZ-DM, although superoxide was higher, suggesting impaired antioxidant response. The increase in ROS before differences in atherosclerosis supports ROS as an initiating event in diabetic vascular disease. Further studies are needed to determine if increases in iron stores and arterial iron deposition promote hydroxyl radical formation from superoxide and accelerate diabetic vascular damage.

Influences of diabetes on the development and progression of cardiovascular disease

Introduction The prevalence of type 2 diabetes mellitus is increasing rapidly worldwide, and by 2030 this insidious condition may well affect 438 million individuals, though this may still be an underestimate. Diabetes mellitus is also a considerable public health concern and more aggressive management of the condition and its complications, particularly cardiovascular disease, is warranted. This dramatic situation requires a more profound understanding of pathophysiological conditions preceding vascular damage in diabetes, the identification and adaptation of new and innovative diagnostic strategies in selecting diabetic patients at high cardiovascular risk and last but not least of course the development and availability of effective and safe drugs for blood glucose control and for the reduction of vascular risk. The March/April 2010 issue of our journal focuses on all three aspects and discusses the management of cardiovascular complications in diabetes. This provides me with the opportunity to introduce myself as a new member of the editorial team of the British Journal of Diabetes & Vascular Disease with primary responsibility for cardiovascular topics.

VEGF-induced choroidal damage in a murine model of retinal neovascularisation

Background/aims:Photoreceptor-specific upregulation of vascular endothelial growth factor (VEGF) in a transgenic mouse model (Kimba) of retinal neovascularisation induces retinal vascular damage which appears similar to that in diabetic retinopathy. Here...

Focus on Molecules: Interphotoreceptor retinoid-binding protein (IRBP)

Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.