Vascular Inflammation In Diabetes Research Articles

Supplementation of Clostridium butyricum Alleviates Vascular Inflammation in Diabetic Mice.

Gut microbiota is closely related to the occurrence and development of diabetes and affects the prognosis of diabetic complications, and the underlying mechanisms are only partially understood. We aimed to explore the possible link between the gut microbiota and vascular inflammation of diabetic mice. The db/db diabetic and wild-type (WT) mice were used in this study. We profiled gut microbiota and examined the and vascular function in both db/db group and WT group. Gut microbiota was analyzed by 16s rRNA sequencing. Vascular function was examined by ultrasonographic hemodynamics and histological staining. Clostridium butyricum (CB) was orally administered to diabetic mice by intragastric gavage every 2 days for 2 consecutive months. Reactive oxygen species (ROS) and expression of nuclear factor erythroid-derived 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were detected by fluorescence microscopy. The mRNA expression of inflammatory cytokines was tested by quantitative polymerase chain reaction. Compared with WT mice, CB abundance was significantly decreased in the gut of db/db mice, together with compromised vascular function and activated inflammation in the arterial tissue. Meanwhile, ROS in the vascular tissue of db/db mice was also significantly increased. Oral administration of CB restored the protective microbiota, and protected the vascular function in the db/db mice via activating the Nrf2/HO-1 pathway. This study identified the potential link between decreased CB abundance in gut microbiota and vascular inflammation in diabetes. Therapeutic delivery of CB by gut transplantation alleviates the vascular lesions of diabetes mellitus by activating the Nrf2/HO-1 pathway.

Platelet-derived calpain cleaves the endothelial protease-activated receptor 1 to induce vascular inflammation in diabetes

Diabetes mellitus is a major risk factor for cardiovascular disease. Platelets from diabetic patients are hyperreactive and release microparticles that carry activated cysteine proteases or calpains. Whether platelet-derived calpains contribute to the development of vascular complications in diabetes is unknown. Here we report that platelet-derived calpain1 (CAPN1) cleaves the protease-activated receptor 1 (PAR-1) on the surface of endothelial cells, which then initiates a signaling cascade that includes the activation of the tumor necrosis factor (TNF)-α converting enzyme (TACE). The latter elicits the shedding of the endothelial protein C receptor and the generation of TNF-α, which in turn, induces intracellular adhesion molecule (ICAM)-1 expression to promote monocyte adhesion. All of the effects of CAPN1 were mimicked by platelet-derived microparticles from diabetic patients or from wild-type mice but not from CAPN1−/− mice, and were not observed in PAR-1-deficient endothelial cells. Importantly, aortae from diabetic mice expressed less PAR-1 but more ICAM-1 than non-diabetic mice, effects that were prevented by treating diabetic mice with a calpain inhibitor as well as by the platelet specific deletion of CAPN1. Thus, platelet-derived CAPN1 contributes to the initiation of the sterile vascular inflammation associated with diabetes via the cleavage of PAR-1 and the release of TNF-α from the endothelial cell surface.

Preventive effect of cocoa flavanols against glucotoxicity-induced vascular inflammation in the arteria of diabetic rats and on the inflammatory process in TNF-α-stimulated endothelial cells

Hyperglycaemia induces a vascular inflammatory process that is a critical event in cardiovascular disease in type 2 diabetes. Cocoa and its flavanols have been widely investigated for its antioxidant and anti-inflammatory properties, and several clinical and pre-clinical studies support their vascular benefits. However, the effects of cocoa flavanols on vascular inflammation in diabetes remains to be elucidated. Herein, we evaluated the anti-inflammatory effect of a cocoa-rich diet on the aortas of Zucker diabetic fatty (ZDF) rats. Moreover, the potential role of flavanol-derived colonic metabolites to modulate the adhesion and inflammatory processes were also evaluated using TNF-α-stimulated endothelial cells. Results demonstrate that cocoa attenuates the levels of phospho-p65-nuclear factor-kappaB (NF-κB) and the expression of inflammatory factors including intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1) and inducible nitric oxide synthase in the aortas of ZDF rats. Experiments with endothelial cells further confirm that a mix of flavanol-derived colonic metabolites effectively down-regulate the levels of p-p65-NF-κB and the cell adhesion molecules ICAM-1 and VCAM-1, preventing thus the increase of monocyte-endothelial adhesion induced by TNF-α. These novel data provide the first evidence of the relevant role of cocoa and their flavanol-derived metabolites to avoid the development of endothelial inflammation and diabetic complications.

Thrombosis and Vascular Inflammation in Diabetes: Mechanisms and Potential Therapeutic Targets.

Cardiovascular disease remains the main cause of morbidity and mortality in patients with diabetes. The risk of vascular ischemia is increased in this population and outcome following an event is inferior compared to individuals with normal glucose metabolism. The reasons for the adverse vascular profile in diabetes are related to a combination of more extensive atherosclerotic disease coupled with an enhanced thrombotic environment. Long-term measures to halt the accelerated atherosclerotic process in diabetes have only partially addressed vascular pathology, while long-term antithrombotic management remains largely similar to individuals without diabetes. We address in this review the pathophysiological mechanisms responsible for atherosclerosis with special emphasis on diabetes-related pathways. We also cover the enhanced thrombotic milieu, characterized by increased platelet activation, raised activity of procoagulant proteins together with compromised function of the fibrinolytic system. Potential new therapeutic targets to reduce the risk of atherothrombosis in diabetes are explored, including alternative use of existing therapies. Special emphasis is placed on diabetes-specific therapeutic targets that have the potential to reduce vascular risk while keeping an acceptable clinical side effect profile. It is now generally acknowledged that diabetes is not a single clinical entity but a continuum of various stages of the condition with each having a different vascular risk. Therefore, we propose that future therapies aiming to reduce vascular risk in diabetes require a stratified approach with each group having a “stage-specific” vascular management strategy. This “individualized care” in diabetes may prove to be essential to improve vascular outcome in this high risk population.

Methylglyoxal-derived hydroimidazolone-1 evokes inflammatory reactions in endothelial cells via an interaction with receptor for advanced glycation end products.

Glyceraldehyde-derived advanced glycation end products contribute to vascular inflammation in diabetes. However, what advanced glycation end product structure could evoke inflammatory reactions remains unknown. We examined whether and how methylglyoxal-derived hydroimidazolone 1, one of the advanced glycation end products formed from glyceraldehyde, elicits inflammatory reactions in human umbilical vein endothelial cells. Glyceraldehyde-advanced glycation end products-aptamer was prepared using a systemic evolution of ligands by exponential enrichment. The binding affinities of methylglyoxal-derived hydroimidazolone 1 to receptor for advanced glycation end products or advanced glycation end product-aptamer were measured with a quartz crystal microbalance. Intracellular reactive oxygen species generation and THP-1 cell adhesion were evaluated using fluorescent probes. Gene expression was analysed by reverse transcription polymerase chain reaction. Methylglyoxal-derived hydroimidazolone 1 bound to receptor for advanced glycation end products and advanced glycation end product-aptamer with a dissociation constant ( Kd) of 56.7 µM and 1.51 mM, respectively. Methylglyoxal-derived hydroimidazolone 1 at 100 µg/mL significantly increased reactive oxygen species generation in human umbilical vein endothelial cells, which were attenuated by anti-receptor for advanced glycation end products antibody or advanced glycation end product-aptamer. In all, 100 µg/mL methylglyoxal-derived hydroimidazolone 1 significantly increased receptor for advanced glycation end products and intercellular adhesion molecule-1 messenger RNA levels in, and THP-1 cell adhesion to, human umbilical vein endothelial cells, all of which were blocked by anti-receptor for advanced glycation end products antibody. Our present results indicate that methylglyoxal-derived hydroimidazolone 1 evokes inflammatory reactions in human umbilical vein endothelial cells via receptor for advanced glycation end products, although apparently limited to supraphysiological levels of methylglyoxal-derived hydroimidazolone 1. Methylglyoxal-derived hydroimidazolone 1 is a distinct advanced glycation end product structure that could mediate harmful effects of methylglyoxal and glyceraldehyde-mediated glycation processes.

Transcriptional Mechanisms that Mediate Downregulation of TSP‐1 by Chromium in Vascular Smooth Muscle Cells in Response to High Glucose

Trivalent chromium (Cr3+) is a beneficial mineral nutrient reported to lower the atherogenic index and reduce risks of vascular inflammation in diabetes. We recently reported that Cr3+ inhibits expression of a proatherogenic matricellular protein, thrombospondin‐1 (TSP‐1), in glucose‐stimulated human aortic smooth muscle cells (HASMC) in vitro. Using luciferase reporter assays, we further showed that Cr3+ significantly decreases TSP‐1 gene (THBS1) promoter activity in glucose‐stimulated cells. The goal of this study was to determine the molecular mechanisms by which Cr3+ inhibits high glucose‐induced TSP‐1 transcription in HASMC. Using protein DNA array (Panomics) that allows detection of activated transcription factors (TF) in nuclear extracts, we demonstrate that Cr3+ reduces activation of glucose‐induced TFs (IRF1, PPARγ), with predicted binding sites in the glucose‐responsive region of the THBS1 promoter. In contrast, Cr3+ did not have any effect on other glucose‐activated TFs (AhR, CEBP, Egr‐1) under similar experimental conditions. These results were further confirmed in EMSA using relevant THBS1 promoter‐specific oligonucleotide probes; specifically we show that Cr3+ attenuates THBS1 promoter‐specific IRF1 binding activity in glucose‐treated nuclear extracts. Additionally, immunoprecipitation of cell lysates with anti‐IRF1 followed by immunoblotting with RL2, an antibody that recognizes O‐linked N‐acetylglucosamine (O‐GlcNAc) moieties on proteins, shows a dramatic reduction in O‐GlcNAcylation of IRF1 by Cr3+ in glucose‐stimulated cells. Together, our data suggest that modulation of IRF1 via O‐GlcNAc modification plays a key role in downregulation of TSP‐1 transcription by Cr3+.

Trivalent chromium inhibits TSP-1 expression, proliferation, and O-GlcNAc signaling in vascular smooth muscle cells in response to high glucose in vitro.

Trivalent chromium (Cr(3+)) is a mineral nutrient reported to have beneficial effects in glycemic and cardiovascular health. In vitro and in vivo studies suggest that Cr(3+) supplementation reduces the atherogenic potential and lowers the risk of vascular inflammation in diabetes. However, effects of Cr(3+) in vascular cells under conditions of hyperglycemia, characteristic of diabetes, remain unknown. In the present study we show that a therapeutically relevant concentration of Cr(3+) (100 nM) significantly downregulates a potent proatherogenic matricellular protein, thrombospondin-1 (TSP-1), in human aortic smooth muscle cells (HASMC) stimulated with high glucose in vitro. Promoter-reporter assays reveal that this downregulation of TSP-1 expression by Cr(3+) occurs at the level of transcription. The inhibitory effects of Cr(3+) on TSP-1 were accompanied by significant reductions in O-glycosylation of cytoplasmic and nuclear proteins. Using Western blotting and immunofluorescence studies, we demonstrate that reduced protein O-glycosylation by Cr(3+) is mediated via inhibition of glutamine: fructose 6-phosphate amidotransferase, a rate-limiting enzyme of the hexosamine pathway, and O-linked N-acetylglucosamine (O-GlcNAc) transferase, a distal enzyme in the pathway that controls intracellular protein O-glycosylation. Additionally, we found that Cr(3+) attenuates reactive oxygen species formation in glucose-stimulated HASMC, suggesting an antioxidant effect. Finally, we report an antiproliferative effect of Cr(3+) that is specific for high glucose and conditions triggering elevated protein O-glycosylation. Taken together, these findings provide the first cellular evidence for a novel role of Cr(3+) to modulate aberrant vascular smooth muscle cell function associated with hyperglycemia-induced vascular complications.

The role of the immune system in the pathogenesis of diabetic complications.

The main causes of morbidity and mortality in diabetes are macrovascular and microvascular complications. The pathogenesis of these complications is multifactorial, but there is strong evidence implicating chronic, smoldering, and inflammation as a main pathogenic event in the development of diabetic complications (1). Although the mechanisms responsible for vascular inflammation in diabetes are similar to those involved in vascular disease in non-diabetics (2), chronic hyperglycemia and dysregulated immune responses in diabetes are responsible for the activation of inflammatory circuits, inducing oxidative stress and promoting insulin resistance (1, 3), thus creating conditions that lead to the development of diabetes and diabetic complications. Changes in gene expression associated with diabetes like increased ICAM-1 expression (4) may also play a role in inducing inflammation and the development of diabetic complications.

Abstract 645: Atheroprotective Mechanism of Chromium Picolinate in Streptozotocin-Induced Diabetic ApoE-/- Mice

Vascular disease accounts for increased morbidity and mortality in diabetes. Given the burden of health care expenditure in diabetics, relatively cost-effective strategies represent an attractive therapeutic approach. Trivalent chromium (Cr) is a mineral nutrient reported to have a beneficial role in glycemic and cardiovascular health. While previous studies suggest that Cr reduces vascular inflammation in diabetes, the precise mechanisms of Cr action in the large blood vessels in diabetes remain unknown. We showed earlier that Cr picolinate (CrP, a bioavailable form of Cr) in vitro downregulates a potent proatherogenic matricellular protein thrombospondin-1 (TSP-1) in glucose-stimulated vascular smooth muscle cells. The present study provides the first evidence of an atheroprotective mechanism of Cr in vivo in a mouse model of diabetic atherosclerosis. Briefly, hyperglycemia was induced in male ApoE -/- mice (6wks age) with 50mg/Kg/day streptozotocin (STZ), i.p. for 5 consecutive days. Hyperglycemic mice (blood glucose>250mg/dl) on regular chow diet were treated with or without CrP (8μg/Kg) in drinking water starting at 8 wks of age and all mice were sacrificed at 18 wks of age. Using en face atherosclerotic lesion assay shown by Oil red O staining, we demonstrated that CrP in vivo significantly prevents development of lesion in aortic vessel walls of hyperglycemic STZ-ApoE -/- mice compared to untreated STZ-ApoE -/- mice. Consistently, high-frequency ultrasound imaging of common carotid artery revealed that CrP prevents development of vascular lesions in STZ-ApoE -/- mice while untreated mice showed more pronounced lesions with a significant reduction (20%) in carotid artery diameter. Importantly, atheroprotective effects of CrP were accompanied by a significant decrease (>35%) in TSP-1 and PCNA (proliferation marker) expression in aortic vessels of STZ-ApoE -/- mice, shown by immunoblotting. Also, en face studies showed that knockout of TSP-1 protects STZ-induced hyperglycemic ApoE -/- mice against atherosclerosis. Together, our results suggest that CrP in vivo prevents diabetic atherosclerosis via downregulation of TSP-1 in the large blood vessel wall, underscoring TSP-1 as a novel therapeutic target in diabetic atherosclerosis.

Manganese supplementation increases adiponectin secretion by upregulating disulfide bond A‐like protein in endothelial cells and Zucker diabetic fatty rats (767.13)

Adiponectin is an insulin sensitizer that plays a role in the regulation of lipid and glucose homeostasis and has anti atherosclerotic effects. It is synthesized as a single polypeptide and is then assembled in the endoplasmic reticulum into different multimers. An adiponectin‐interacting protein named disulfide bond A‐like protein (DsbA‐L) was recently found to play an important role in multimerization of adiponectin; impairment in DsbA‐L is associated with diabetes and low adiponectin levels. Manganese (Mn) levels have been found to be low in atherosclerotic and diabetic patients. Previous studies in our lab have shown that Mn supplementation can lower blood cholesterol and ICAM‐1 levels in ZDF rats and reduce MCP‐1 secretion and monocyte adhesion to endothelial cells in HUVECs model (J. Biol. Chem, 2013 Mar 1; 288 (9):6409‐16). This study investigates the hypothesis that Mn supplementation affects DsbA‐L expression levels, and thereby adiponectin levels, in ZDF rats and endothelial cells (HUVECs). Results show that diabetic rats supplemented with Mn (gavaged daily with 16 mg/kg BW for seven weeks, n=5) have higher plasma adiponectin levels (41%, p=0.007) and higher DsbA‐L expression in the liver compared to control diabetic rats (n=6). Similarly, pre‐treatment with Mn (with 5 or 10 μM for 24 h) prevented the decrease in DsbAL expression and adiponectin levels in HUVECs and 3T3L1 adipocyte cells exposed to high glucose and MCP‐1. We further investigated the role of DsbA‐L protein by knocking down its expression in HUVECs. Preliminary studies with DsbA‐L siRNA show that beneficial effects of Mn supplementation on NOX4 expression and other biomarkers of vascular inflammation were abolished in DsbA‐L knocked down cells. Thus, this study demonstrates that DsbA‐L mediates the beneficial effects of Mn on adiponectin and provides a novel mechanism by which Mn supplementation reduces biomarkers of vascular inflammation in diabetes.

Manganese supplementation increases adiponectin secretion by upregulating disulfide bond A‐like protein in endothelial cells and Zucker diabetic fatty rats (249.1)

Adiponectin is an insulin sensitizer that plays a role in the regulation of lipid and glucose homeostasis and has anti atherosclerotic effects. It is synthesized as a single polypeptide and is then assembled in the endoplasmic reticulum into different multimers. An adiponectin‐interacting protein named disulfide bond A‐like protein (DsbA‐L) was recently found to play an important role in multimerization of adiponectin; impairment in DsbA‐L is associated with diabetes and low adiponectin levels. Manganese (Mn) levels have been found to be low in atherosclerotic and diabetic patients. Previous studies in our lab have shown that Mn supplementation can lower blood cholesterol and ICAM‐1 levels in ZDF rats and reduce MCP‐1 secretion and monocyte adhesion to endothelial cells in HUVECs model (J. Biol. Chem, 2013 Mar 1; 288 (9):6409‐16). This study investigates the hypothesis that Mn supplementation affects DsbA‐L expression levels, and thereby adiponectin levels, in ZDF rats and endothelial cells (HUVECs). Results show that diabetic rats supplemented with Mn (gavaged daily with 16 mg/kg BW for seven weeks, n=5) have higher plasma adiponectin levels (41%, p=0.007) and higher DsbA‐L expression in the liver compared to control diabetic rats (n=6). Similarly, pre‐treatment with Mn (with 5 or 10 μM for 24 h) prevented the decrease in DsbAL expression and adiponectin levels in HUVECs and 3T3L1 adipocyte cells exposed to high glucose and MCP‐1. We further investigated the role of DsbA‐L protein by knocking down its expression in HUVECs. Preliminary studies with DsbA‐L siRNA show that beneficial effects of Mn supplementation on NOX4 expression and other biomarkers of vascular inflammation were abolished in DsbA‐L knocked down cells. Thus, this study demonstrates that DsbA‐L mediates the beneficial effects of Mn on adiponectin and provides a novel mechanism by which Mn supplementation reduces biomarkers of vascular inflammation in diabetes.

L-cysteine and hydrogen sulfide increase PIP3 and AMPK/PPARγ expression and decrease ROS and vascular inflammation markers in high glucose treated human U937 monocytes

Diabetic patients have lower blood levels of L-cysteine (LC) and hydrogen sulfide (H2 S) and a higher incidence of vascular inflammation. This study examined whether impaired LC or H2S levels affect vascular inflammation markers in diabetes. Human U937 monocytic cells were treated with high-glucose (HG, 25 mM, 20 h) in the presence or absence of LC (100, 500, or 1,000 µM, an endogenous precursor of H2 S) or Na2S (5 or 25 µM, an exogenous source of H2S). Both LC and Na2 S supplementation decreased intracellular ROS production and increased cellular PIP3 (phosphatidylinositol-3,4,5-trisphosphate) in HG-exposed cells. The effect of LC on PIP3 was prevented by propargylglycine, an inhibitor of cystathionine-γ-lyase (CSE) that catalyzes H2S formation from LC. Signal silencing studies with CSE siRNA also showed the inhibition of H2S formation and PIP3 upregulation in LC-supplemented CSE knockdown cells exposed to HG. This demonstrates that H2S plays a role in mediating the effect of LC on increased PIP3. Using the PI3K specific inhibitor LY294002, this study demonstrated that PI3K activation mediates the effect of LC and Na2S on PIP3 upregulation. Results showed that supplementation with LC and Na2S reduced NF-κB phosphorylation and the secretion of TNF-α, MCP-1, IL-8, IL-1β, and IP-10. Treatment with LC (500 µM), Na2S (25 µM), and PIP3 (5 nM) increased the AMPK phosphorylation and PPARγ expression in cells exposed to HG. This study reports for the first time a novel molecular mechanism by which Na2S or LC supplementation can lower oxidative stress and various markers of vascular inflammation in diabetes.

Epigallocatechin gallate reduces vascular inflammation in db/db mice possibly through an NF‐κB‐mediated mechanism

Hyperglycemia-induced vascular inflammation resulting in the adhesion of monocytes to endothelium is a key event in the pathogenesis of atherosclerosis in diabetes. We investigated whether epigallocatechin gallate (EGCG), a major catechin found in green tea, reduces vascular inflammation in diabetes. Human aortic endothelial cells (HAEC) were pretreated with green tea catechins before the addition of high glucose (25 mM) for 72 h. EGCG at physiologically achievable concentration (1 μM) significantly inhibited high glucose induced adhesion of monocytes to HAEC both in static and under flow conditions. EGCG also reduced nuclear factor κB (NF-κB) regulated transcriptional activity in ECs. Six-week-old diabetic db/db mice were fed a diet containing 0% or 0.1% EGCG for 8 weeks. ECs were isolated from aortic vessels of db/db, db/db-EGCG, and control db/+ mice. EGCG supplementation greatly suppressed diabetes-increased monocytes adhesion to ECs, which is associated with reduced circulating levels of chemokines, and reduced secretions of chemokines and adhesion molecules by aortic ECs from db/db-EGCG mice. EGCG treatment reduced nuclear translocation of NF-κB p65 in aortic vessels, decreased blood pressure and serum concentrations of cholesterol and triglycerides in db/db-EGCG mice. EGCG may have a direct protective effect against vascular inflammation in diabetes.

Toll-like receptor-4 and vascular inflammation in diabetes: Editorial

Toll-like receptor-4 and vascular inflammation in diabetes: Editorial

Human Vascular Endothelial Cells: A Model System for Studying Vascular Inflammation in Diabetes and Atherosclerosis

The vascular endothelium is the inner lining of blood vessels serving as autocrine and paracrine organ that regulates vascular wall function. Endothelial dysfunction is recognized as initial step in the atherosclerotic process and is well advanced in diabetes, even before the manifestation of end-organ damage. Strategies capable of assessing changes in vascular endothelium at the preclinical stage hold potential to refine cardiovascular risk. In vitro cell culture is useful in understanding the interaction of endothelial cells with various mediators; however, it is often criticized due to the uncertain relevance of results to humans. Although circulating endothelial cells, endothelial microparticles, and progenitor cells opened the way for ex vivo studies, a recently described method for obtaining primary endothelial cells through endovascular biopsy allows direct characterization of endothelial phenotype in humans. In this article, we appraise the use of endothelial cell-based methodologies to study vascular inflammation in diabetes and atherosclerosis.

L-Cysteine supplementation lowers blood glucose, glycated hemoglobin, CRP, MCP-1, and oxidative stress and inhibits NF-κB activation in the livers of Zucker diabetic rats

This study examined the hypothesis that l-cysteine supplementation can lower insulin resistance, glycemia, oxidative stress, and markers of vascular inflammation in type 2 diabetes using Zucker diabetic fatty (ZDF) rats as a model. Starting at the age of 6 weeks, ZDF rats were supplemented orally (daily gavage, 8 weeks) with saline placebo (D) or l-cysteine (LC; 1 mg/kg bw) and fed a high-calorie diet. Six-week-old rats without any supplementation were considered baseline (BL) rats. D rats showed elevated fasting blood glucose, glycated Hb, CRP, and MCP-1 compared with BL rats in which there was no onset of diabetes. LC supplementation significantly lowered blood levels of glucose (18%, p = 0.05), glycated Hb (8%, p = 0.02), CRP (23%, p = 0.02), MCP-1 (32%, p = 0.01), and insulin resistance (25%) compared with levels seen in saline-supplemented D rats. There was a decrease in plasma protein oxidation levels ( p < 0.01); however, GSH levels were similar in LC and D groups. Although LC did not change blood hematocrit or levels of transaminases, it did lower alkaline phosphatase (29%, p = 0.01) levels in comparison to D. Western blotting analyses of liver showed increased activation of NF-κB and Akt (50% pNF-κB and 20% pAkt) in D compared with BL rats. LC supplementation inhibited these effects (17% pAkt, 18% pNF-κB). This is the first report showing that l-cysteine supplementation can lower glycemia and markers of vascular inflammation in diabetes apparently by preventing NF-κB activation in a diabetic animal model.

Curcumin Supplementation Lowers TNF-α, IL-6, IL-8, and MCP-1 Secretion in High Glucose-Treated Cultured Monocytes and Blood Levels of TNF-α, IL-6, MCP-1, Glucose, and Glycosylated Hemoglobin in Diabetic Rats

This study examined the hypothesis that curcumin supplementation decreases blood levels of IL-6, MCP-1, TNF-alpha, hyperglycemia, and oxidative stress by using a cell-culture model and a diabetic rat model. U937 monocytes were cultured with control (7 mM) and high glucose (35 mM) in the absence or presence of curcumin (0.01-1 microM) at 37 degrees C for 24 h. Diabetes was induced in Sprague-Dawley rats by injection of streptozotocin (STZ) (i.p., 65 mg/kg BW). Control buffer, olive oil, or curcumin (100 mg/kg BW) supplementation was administered by gavage daily for 7 weeks. Blood was collected by heart puncture with light anesthesia. Results show that the effect of high glucose on lipid peroxidation, IL-6, IL-8, MCP-1, and TNF-alpha secretion was inhibited by curcumin in cultured monocytes. In the rat model, diabetes caused a significant increase in blood levels of IL-6, MCP-1, TNF-alpha, glucose, HbA(1), and oxidative stress, which was significantly decreased in curcumin-supplemented rats. Thus, curcumin can decrease markers of vascular inflammation and oxidative stress levels in both a cell-culture model and in the blood of diabetic rats. This suggests that curcumin supplementation can reduce glycemia and the risk of vascular inflammation in diabetes.

Endothelial dysfunction and vascular inflammation in Type 2 diabetes: interaction of AGE/RAGE and TNF-α signaling

the receptor for advanced glycation end products (RAGE) interacts with a diverse range of endogenous ligands termed advanced glycation end products (AGEs), which are formed by the Maillard reaction, a nonenzymatic process linking reducing sugar groups to proteins, lipids, and nucleic acids. AGEs

Abstract 243: Roles of TNF alpha and MCP-1 in Type II Diabetes-induced Endothelial Dysfunction

Tumor necrosis factor alpha (TNF) is reported to underlie a component of vascular inflammation and ensuing endothelial dysfunction in diabetes, but the role of inflammatory cells in these events is unknown. Because TNF reportedly induces monocyte chemoattractant protein-1 (MCP-1) expression, we hypothesized that the interaction between TNF and MCP-1 contributes to the evolution of vascular inflammation in diabetes. To test this hypothesis, expression of TNF and MCP-1, and formation of nitrotyrosine (N-Tyr, an indicator of peroxynitrite production) were determined in isolated coronary arterioles (50–100um) from genetically modified mice with Type II diabetes (Lepr db ) and the lean control heterozygotes (m Lepr db ). Protein and mRNA expression of TNF, protein expression of MCP-1, and presence of N-Tyr were significantly increased in arterioles from Lepr db mice compared to those from m Lepr db . Immunofluorescence double labeling revealed the prominent localization of MCP-1 to endothelium (Von Willebrand factor) of arterioles and venules. MCP-1 also co-localized with macrophages (CD68) in the heart tissue. To determine if MCP-1 may be key to the vascular inflammation and ensuing endothelial dysfunction, we administered anti-MCP-1 (10 μg/day, 3 days, i.p., n=4; to block MCP-1 signaling) in the mice and then determined endothelial dilation in isolated, cannulated pressurized (60 cmH2O) arterioles. Anti-MCP-1 restored dilation to acetylcholine in Lepr db mice by 35±2% (P&lt;0.05 vs Lepr db mice without treatment, 9.8±4%) but did not affect dilation in m Lepr db mice. To establish interactions between TNF and MCP-1, we administered anti-TNF (72hr treatment; 0.625mg/kg, i.p.) to block TNF signaling and determined effects on MCP-1 and oxidative stress. After anti-TNF administration, expression of MCP-1 was decreased and numbers of MCP-1 positive cells were markedly reduced in Lepr db mice. Moreover, anti-TNF prevented the formation of N-Tyr in Lepr db mice. These findings demonstrate that the endothelial dysfunction occurring in type II diabetes is the result of the effects of the inflammatory cytokine TNF and TNF related signaling, including the expression of MCP-1, which also furthers the oxidative stress.

The endothelium and vascular inflammation in diabetes

The endothelium releases multiple mediators, not only regulators of vasomotor function but also important physiological and pathophysiological inflammatory mediators. Endothelial dysfunction is caused by chronic exposure to various stressors such as oxidative stress and modified low-density lipoprotein (LDL) cholesterol, resulting in impaired nitric oxide (NO) production and chronic inflammation. Biomechanical forces on the endothelium, including low shear stress from disturbed blood flow and hypertension, are also important causes of endothelial dysfunction. These processes seem to be augmented in patients with diabetes. In states of insulin resistance and in type 2 diabetes insulin signalling is impaired. Increased vascular inflammation, including enhanced expression of interleukin- 6 (IL-6), vascular cellular adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein (MCP- 1) are observed, as is a marked decrease in NO bioavailability. Furthermore, hyperglycaemia leads to increased formation of advanced glycation end products (AGE), which quench NO and impair endothelial function. In summary, during the development of diabetes a number of biochemical and mechanical factors converge on the endothelium, resulting in endothelial dysfunction and vascular inflammation. In the presence of insulin resistance, these processes are potentiated and they provide a basis for the macrovascular disease seen in diabetes.