High glucose-induced apoptosis in human coronary artery endothelial cells involves up-regulation of death receptors

The research progress of crosstalk mechanism of autophagy and apoptosis in diabetic vascular endothelial injury

In recent years, the widespread prevalence of diabetes has become a major killer that threatens the health of people worldwide. Of particular concern is hyperglycemia-induced vascular endothelial injury, which is one of the factors that aggravate diabetic vascular disease. During the process of diabetic vascular endothelial injury, apoptosis is an important pathological manifestation and autophagy is a key regulatory mechanism. Autophagy and apoptosis interact with each other. Hence, the crosstalk mechanism between the two processes is an important means of regulating diabetic vascular endothelial injury. This article reviews the research progress in apoptosis in the context of diabetic vascular endothelial injury and discusses the crosstalk mechanism of autophagy and apoptosis and its role in this injury. The purpose is to guide the prevention and treatment of diabetic vascular endothelial injury in the future.

Restoration of coronary microvascular function by OGA overexpression in a high-fat diet with low-dose streptozotocin-induced type 2 diabetic mice

Sustained hyperglycemia results in excess protein O-GlcNAcylation, leading to vascular complications in diabetes. This study aims to investigate the role of O-GlcNAcylation in the progression of coronary microvascular disease (CMD) in inducible type 2 diabetic (T2D) mice generated by a high-fat diet with a single injection of low-dose streptozotocin. Inducible T2D mice exhibited an increase in protein O-GlcNAcylation in cardiac endothelial cells (CECs) and decreases in coronary flow velocity reserve (CFVR, an indicator of coronary microvascular function) and capillary density accompanied by increased endothelial apoptosis in the heart. Endothelial-specific O-GlcNAcase (OGA) overexpression significantly lowered protein O-GlcNAcylation in CECs, increased CFVR and capillary density, and decreased endothelial apoptosis in T2D mice. OGA overexpression also improved cardiac contractility in T2D mice. OGA gene transduction augmented angiogenic capacity in high-glucose treated CECs. PCR array analysis revealed that seven out of 92 genes show significant differences among control, T2D, and T2D + OGA mice, and Sp1 might be a great target for future study, the level of which was significantly increased by OGA in T2D mice. Our data suggest that reducing protein O-GlcNAcylation in CECs has a beneficial effect on coronary microvascular function, and OGA is a promising therapeutic target for CMD in diabetic patients.

Epigenetic Changes Induced by High Glucose in Human Pancreatic Beta Cells

Epigenetic changes in pancreatic beta cells caused by sustained high blood glucose levels, as seen in prediabetic conditions, may contribute to the etiology of diabetes. To delineate a direct cause and effect relationship between high glucose and epigenetic changes, we cultured human pancreatic beta cells derived from induced pluripotent stem cells and treated them with either high or low glucose, for 14 days. We then used the Arraystar 4x180K HG19 RefSeq Promoter Array to perform whole-genome DNA methylation analysis. A total of 478 gene promoters, out of a total of 23,148 present on the array (2.06%), showed substantial differences in methylation (p < 0.01). Out of these, 285 were hypomethylated, and 193 were hypermethylated in experimental vs. control. Ingenuity Pathway Analysis revealed that the main pathways and networks that were differentially methylated include those involved in many systems, including those related to development, cellular growth, and proliferation. Genes implicated in the etiology of diabetes, including networks involving glucose metabolism, insulin secretion and regulation, and cell cycle regulation, were notably altered. Influence of upstream regulators such as MRTFA, AREG, and NOTCH3 was predicted based on the altered methylation of their downstream targets. The study validated that high glucose levels can directly cause many epigenetic changes in pancreatic beta cells, suggesting that this indeed may be a mechanism involved in the etiology of diabetes.

Design considerations of benchtop fluid flow bioreactors for bio-engineered tissue equivalents in vitro

One of the major aims of bio-engineering tissue equivalents in vitro is to create physiologically relevant culture conditions to accurately recreate the cellular microenvironment. This often includes incorporation of factors such as the extracellular matrix, co-culture of multiple cell types and three-dimensional culture techniques. These advanced techniques can recapitulate some of the properties of tissue in vivo, however fluid flow is a key aspect that is often absent. Fluid flow can be introduced into cell and tissue culture using bioreactors, which are becoming increasingly common as we seek to produce increasingly accurate tissue models. Bespoke technology is continuously being developed to tailor systems for specific applications and to allow compatibility with a range of culture techniques. For effective perfusion of a tissue culture many parameters can be controlled, ranging from impacts of the fluid flow such as increased shear stress and mass transport, to potentially unwanted side effects such as temperature fluctuations. A thorough understanding of these properties and their implications on the culture model can aid with a more accurate interpretation of results. Improved and more complete characterisation of bioreactor properties will also lead to greater accuracy when reporting culture conditions in protocols, aiding experimental reproducibility, and allowing more precise comparison of results between different systems. In this review we provide an analysis of the different factors involved in the development of benchtop flow bioreactors and their potential biological impacts across a range of applications.

Multi-omics study identifies novel signatures of DNA/RNA, amino acid, peptide, and lipid metabolism by simulated diabetes on coronary endothelial cells

Coronary artery endothelial cells (CAEC) exert an important role in the development of cardiovascular disease. Dysfunction of CAEC is associated with cardiovascular disease in subjects with type 2 diabetes mellitus (T2DM). However, comprehensive studies of the effects that a diabetic environment exerts on this cellular type are scarce. The present study characterized the molecular perturbations occurring on cultured bovine CAEC subjected to a prolonged diabetic environment (high glucose and high insulin). Changes at the metabolite and peptide level were assessed by Liquid Chromatography–Mass Spectrometry (LC–MS²) and chemoinformatics. The results were integrated with published LC–MS²-based quantitative proteomics on the same in vitro model. Our findings were consistent with reports on other endothelial cell types and identified novel signatures of DNA/RNA, amino acid, peptide, and lipid metabolism in cells under a diabetic environment. Manual data inspection revealed disturbances on tryptophan catabolism and biosynthesis of phenylalanine-based, glutathione-based, and proline-based peptide metabolites. Fluorescence microscopy detected an increase in binucleation in cells under treatment that also occurred when human CAEC were used. This multi-omics study identified particular molecular perturbations in an induced diabetic environment that could help unravel the mechanisms underlying the development of cardiovascular disease in subjects with T2DM.

Highly perturbed genes and hub genes associated with type 2 diabetes in different tissues of adult humans: a bioinformatics analytic workflow

Type 2 diabetes (T2D) has a complex etiology which is not yet fully elucidated. The identification of gene perturbations and hub genes of T2D may deepen our understanding of its genetic basis. We aimed to identify highly perturbed genes and hub genes associated with T2D via an extensive bioinformatics analytic workflow consisting of five steps: systematic review of Gene Expression Omnibus and associated literature; identification and classification of differentially expressed genes (DEGs); identification of highly perturbed genes via meta-analysis; identification of hub genes via network analysis; and downstream analysis of highly perturbed genes and hub genes. Three meta-analytic strategies, random effects model, vote-counting approach, and p value combining approach, were applied. Hub genes were defined as those nodes having above-average betweenness, closeness, and degree in the network. Downstream analyses included gene ontologies, Kyoto Encyclopedia of Genes and Genomes pathways, metabolomics, COVID-19-related gene sets, and Genotype-Tissue Expression profiles. Analysis of 27 eligible microarrays identified 6284 DEGs (4592 downregulated and 1692 upregulated) in four tissue types. Tissue-specific gene expression was significantly greater than tissue non-specific (shared) gene expression. Analyses revealed 79 highly perturbed genes and 28 hub genes. Downstream analyses identified enrichments of shared genes with certain other diabetes phenotypes; insulin synthesis and action-related pathways and metabolomics; mechanistic associations with apoptosis and immunity-related pathways; COVID-19-related gene sets; and cell types demonstrating over- and under-expression of marker genes of T2D. Our approach provided valuable insights on T2D pathogenesis and pathophysiological manifestations. Broader utility of this pipeline beyond T2D is envisaged.

NIK-SIX1 signalling axis regulates high glucose-induced endothelial cell dysfunction and inflammation

Endothelial dysfunction and inflammation are the main manifestations of diabetes-associated atherosclerosis. This paper studied the roles of NF-κB-inducing kinase (NIK) and sine oculis homeobox homolog 1 (SIX1) in regulating high glucose-induced endothelial dysfunction and inflammation. The expression of NIK and SIX1 in human umbilical vein endothelial cells (HUVECs) was silenced by transfection with the specific shRNAs. HUVECs exposed to high glucose were considered as a cell model of endothelial dysfunction. Expression of NIK and SIX1 following transfection was measured by qRT-PCR and western blotting analysis. The proliferation, migration, and inflammation of HUVECs were evaluated by EdU staining, scratch test, ELISA, and western blotting. High glucose (30 mM) significantly decreased the proliferation and migration of HUVECs. High glucose-induced the expression of adhesion molecules VCAM-1 and ICAM-1. Moreover, high glucose increased the release of IL-1β, IL-6, TNF-α, and MCP-1. Transfection of cells with NIK shRNA significantly reversed the toxic effects of high glucose on HUVECs. Of contrast, SIX1 shRNA accelerated the effects of high glucose on HUVECs. NIK shRNA inhibited the accumulation of RelA, RelB, and p52. Meanwhile, NIK shRNA led to SIX1 downregulation which further induced the activation of the NF-κB pathway. NIK-SIX1 signalling axis was suggested to be critical in the regulation of high glucose-induced endothelial dysfunction and inflammation. SIX1 may function as an immunological gatekeeper to control the excessive inflammation mediated by NIK in diabetes-associated atherosclerosis.

Angiogenic content of microparticles in patients with diabetes and coronary artery disease predicts networks of endothelial dysfunction

BACKGROUND

Elevated endothelial microparticles (EMPs) levels are surrogate markers of vascular dysfunction. We analyzed EMPs with apoptotic characteristics and assessed the angiogenic contents of microparticles in the blood of patients with type 2 diabetes (T2D) according to the presence of coronary artery disease (CAD).

METHODS

A total of 80 participants were recruited and equally classified as (1) healthy without T2D, (2) T2D without cardiovascular complications, (3) T2D and chronic coronary artery disease (CAD), and (4) T2D and acute coronary syndrome (ACS). MPs were isolated from the peripheral circulation, and EMPs were characterized using flow cytometry of CD42 and CD31. CD62E was used to determine EMPs' apoptotic/activation state. MPs content was extracted and profiled using an angiogenesis array.

RESULTS

Levels of CD42- CD31 + EMPs were significantly increased in T2D with ACS (257.5 ± 35.58) when compared to healthy subjects (105.7 ± 12.96, p < 0.01). There was no significant difference when comparing T2D with and without chronic CAD. The ratio of CD42-CD62 +/CD42-CD31 + EMPs was reduced in all T2D patients, with further reduction in ACS when compared to chronic CAD, reflecting a release by apoptotic endothelial cells. The angiogenic content of the full population of MPs was analyzed. It revealed a significant differential expression of 5 factors in patients with ACS and diabetes, including TGF-β1, PD-ECGF, platelet factor 4, serpin E1, and thrombospondin 1. Ingenuity Pathway Analysis revealed that those five differentially expressed molecules, mainly TGF-β1, inhibit key pathways involved in normal endothelial function. Further comparison of the three diabetes groups to healthy controls and diabetes without cardiovascular disease to diabetes with CAD identified networks that inhibit normal endothelial cell function. Interestingly, DDP-IV was the only differentially expressed protein between chronic CAD and ACS in patients with diabetes.

CONCLUSION

Our data showed that the release of apoptosis-induced EMPs is increased in diabetes, irrespective of CAD, ACS patients having the highest levels. The protein contents of MPs interact in networks that indicate vascular dysfunction.

Endothelial Thioredoxin-Interacting Protein Depletion Reduces Hemorrhagic Transformation in Hyperglycemic Mice after Embolic Stroke and Thrombolytic Therapy

We hypothesize that endothelial-specific thioredoxin-interacting protein knock-out (EC-TXNIP KO) mice will be more resistant to the neurovascular damage (hemorrhagic-transformation-HT) associated with hyperglycemia (HG) in embolic stroke. Adult-male EC-TXNIP KO and wild-type (WT) littermate mice were injected with-streptozotocin (40 mg/kg, i.p.) for five consecutive days to induce diabetes. Four-weeks after confirming HG, mice were subjected to embolic middle cerebral artery occlusion (eMCAO) followed by tissue plasminogen activator (tPA)-reperfusion (10 mg/kg at 3 h post-eMCAO). After the neurological assessment, animals were sacrificed at 24 h for neurovascular stroke outcomes. There were no differences in cerebrovascular anatomy between the strains. Infarct size, edema, and HT as indicated by hemoglobin (Hb)-the content was significantly higher in HG-WT mice, with or without tPA-reperfusion, compared to normoglycemic WT mice. Hyperglycemic EC-TXNIP KO mice treated with tPA tended to show lower Hb-content, edema, infarct area, and less hemorrhagic score compared to WT hyperglycemic mice. EC-TXNIP KO mice showed decreased expression of inflammatory mediators, apoptosis-associated proteins, and nitrotyrosine levels. Further, vascular endothelial growth factor-A and matrix-metalloproteinases (MMP-9/MMP-3), which degrade junction proteins and increase blood-brain-barrier permeability, were decreased in EC-TXNIP KO mice. Together, these findings suggest that vascular-TXNIP could be a novel therapeutic target for neurovascular damage after stroke.

The Role of miR-181c in Mechanisms of Diabetes-Impaired Angiogenesis: An Emerging Therapeutic Target for Diabetic Vascular Complications

Diabetes mellitus is estimated to affect up to 700 million people by the year 2045, contributing to an immense health and economic burden. People living with diabetes have a higher risk of developing numerous debilitating vascular complications, leading to an increased need for medical care, a reduced quality of life and increased risk of early death. Current treatments are not satisfactory for many patients who suffer from impaired angiogenesis in response to ischaemia, increasing their risk of ischaemic cardiovascular conditions. These vascular pathologies are characterised by endothelial dysfunction and abnormal angiogenesis, amongst a host of impaired signaling pathways. Therapeutic stimulation of angiogenesis holds promise for the treatment of diabetic vascular complications that stem from impaired ischaemic responses. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis to improve ischaemic complications such as ischaemic heart disease and peripheral artery disease, highlighting the immense unmet need. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis in a clinical setting, highlighting the immense unmet need. MicroRNAs (miRNAs) are emerging as powerful targets for multifaceted diseases including diabetes and cardiovascular disease. This review highlights the potential role of microRNAs as therapeutic targets for rescuing diabetes-impaired angiogenesis, with a specific focus on miR-181c, which we have previously identified as an important angiogenic regulator. Here we summarise the pathways currently known to be regulated by miR-181c, which include the classical angiogenesis pathways that are dysregulated in diabetes, mitochondrial function and axonal guidance, and describe how these relate both directly and indirectly to angiogenesis. The pleiotropic actions of miR-181c across multiple key angiogenic signaling pathways and critical cellular processes highlight its therapeutic potential as a novel target for treating diabetic vascular complications.

Zinc Modulates the Response to Apoptosis in an In Vitro Model with High Glucose and Inflammatory Stimuli in C2C12 Cells

Apoptosis is programmed cell death and its alteration is related to cancer, neurologic, autoimmune, and chronic diseases. A number of factors can affect this process. The aim of this paper is to study the effect of supplemental zinc on apoptosis-related genes in C2C12 myoblast cells after being challenged with a series of stimuli, such as high glucose, insulin, and an inflammatory agent. C2C12 myoblast cells were cultured for 24 h with zinc (Zn) (ZnSO₄) 10 or 100 μM and/or glucose 10 or 30 mM. In addition to these stimuli, the cells were challenged with insulin 1 nM or interleukin-6 (IL-6) 5 nM. The mRNA expression of proapoptotic genes caspase 3 and Fas, the antiapoptotic genes, Xiap and Bcl-xL and the ratio of pro-/antiapoptotic genes Bax/Bcl-2, were determined by qRT-PCR. The expression of caspase-3 gene was significantly increased in the presence of the combination high Zn/high glucose with and without the presence of insulin and IL6 in the culture medium Fas expression instead, showed uneven responses. The expression of Bcl-xL and Xiap was increased in most conditions by having high Zn in the medium regardless of the presence of insulin or IL6. Bax/Bcl2 ratio was decreased in the presence of high Zn. Zn was able to stimulate the expression of antiapoptotic genes. This effect was specially noted in high-glucose conditions with and without the presence of insulin. This effect is partially overridden by the presence of an inflammatory agent such as IL-6.

Hyperoxalemia Leads to Oxidative Stress in Endothelial Cells and Mice with Chronic Kidney Disease

INTRODUCTION

Cardiovascular disease is the most common cause of morbidity and mortality in patients with ESRD. In addition to phosphate overload, oxalate, a common uremic toxin, is also involved in vascular calcification in patients with ESRD. The present study investigated the role and mechanism of hyperoxalemia in vascular calcification in mice with uremia.

METHODS

A uremic atherosclerosis (UA) model was established by left renal excision and right renal electrocoagulation in apoE-/- mice to investigate the relationship between oxalate loading and vascular calcification. After 12 weeks, serum and vascular levels of oxalate, vascular calcification, inflammatory factors (TNF-α and IL-6), oxidative stress markers (malondialdehyde [MDA], and advanced oxidation protein products [AOPP]) were assessed in UA mice. The oral oxalate-degrading microbe Oxalobacter formigenes (O. formigenes) was used to evaluate the effect of a reduction in oxalate levels on vascular calcification. The mechanism underlying the effect of oxalate loading on vascular calcification was assessed in cultured human aortic endothelial cells (HAECs) and human aortic smooth muscle cells (HASMCs).

RESULTS

Serum oxalate levels were significantly increased in UA mice. Compared to the control mice, UA mice developed more areas of aortic calcification and showed significant increases in aortic oxalate levels and serum levels of oxidative stress markers and inflammatory factors. The correlation analysis showed that serum oxalate levels were positively correlated with the vascular oxalate levels and serum MDA, AOPP, and TNF-α levels, and negatively correlated with superoxide dismutase activity. The O. formigenes intervention decreased serum and vascular oxalate levels, while did not improve vascular calcification significantly. In addition, systemic inflammation and oxidative stress were also improved in the O. formigenes group. In vitro, high concentrations of oxalate dose-dependently increased oxidative stress and inflammatory factor expression in HAECs, but not in HASMCs.

CONCLUSIONS

Our results indicated that hyperoxalemia led to the systemic inflammation and the activation of oxidative stress. The reduction in oxalate levels by O. formigenes might be a promising treatment for the prevention of oxalate deposition in calcified areas of patients with ESRD.

Effect of Rosolic acid on endothelial dysfunction under ER stress in pancreatic microenvironment

Endothelial cell (EC) dysfunction is the underlying cause for the development of several pathologies, and the interdependency between the pancreatic β-cells and ECs has been established in the pathophysiology of diabetes. ECs release several factors that govern the expression of genes involved in the proliferation, physiology, and survival of the β-cells. Of the known factors that collapse this intricately balanced system, endothelial dysfunction is the crucial condition that manifests as the causative factor for micro and macrovascular diseases. Our earlier studies demonstrated that activation of nuclear factor erythroid-related factor (Nrf2) renders protection to the ECs experiencing ER stress. In this study, using a co-culture system, the crosstalk between pancreatic cells under ER stress and ECs and the effect of a novel Nrf2 activator Rosolic Acid (RA), on the crosstalk was investigated. ECs pre-treated with different concentrations RA and co-cultured with thapsigargin-induced ER stressed pancreatic β-cells showed increased levels of Nrf2 and its downstream targets such as heme oxygenase-1 (HO-1) and NADPH-quinone oxidoreductase-1 (NQO-1), and reduction of ER stress evinced by the decreased levels of glucose-regulated protein (GRP) 78 and C/ERB homologous protein (CHOP). The sensitization of ECs using RA, offered protection to pancreatic cells against ER stress as displayed by increased intracellular insulin and upregulated expression of cell survival and proliferative genes BCl2 and PDX-1. In addition, RA treatment resulted in elevated levels of various angiogenic factors, while inflammatory (TNF-α and IL-1β) and apoptotic markers (CXCL10 and CCL2) decreased. RA treatment normalized the levels of 115 proteins of the 277, which were differentially regulated as revealed by proteomic studies of ER stressed pancreatic β-cells in co-culture conditions. These findings clearly indicate the role of small molecule activators of Nrf2 not only in restoring the functioning of pancreatic cells but also in increasing the cell mass. Further, the study impinges on the strategies that can be developed to balance the pancreatic microenvironment, leading to the restoration of β-cell mass and their normophysiology in diabetic patients.

Isoliquiritigenin attenuates inflammation and modulates Nrf2/caspase-3 signalling in STZ-induced aortic injury

OBJECTIVES

The current study provides evidence on the ameliorative impact of Isoliquiritigenin (ISL), a natural bioflavonoid isolated from licorice roots against diabetes mellitus (DM)-induced aortic injury in rats.

METHODS

DM was induced in male Sprague-Dawley rats by single I.P. injection of STZ (50 mg/kg). ISL was administrated daily (20 mg/kg, orally) for 8 wks.

KEY FINDINGS

Diabetic group showed a significant aortic injury with evidence of atherosclerotic lesions development. Daily ISL (20 mg/kg, orally) administration for 8 wks significantly restored aortic oxidative/antioxidative stress homeostasis via modulating NrF-2/Keap-1/HO-1. Moreover, ISL treatment restored aortic levels of IL-10 and dampened aortic levels of IL-6 and TNF-α. Caspase-3 expression significantly declined as well. Further, ISL treatment successfully suppressed aortic endothelin-1 (ET-1) expression and restored NO contents, eNOS immunostaining paralleled with retraction in atherosclerotic lesions development, and lipid deposition with histopathological architectural preservation and restoration of almost normal aortic thickness.

CONCLUSION

ISL can be proposed to be an effective protective therapy to prevent progression of DM-induced vascular injury and to preserve aortic integrity.

Inhibition of long noncoding RNA MALAT1 suppresses high glucose-induced apoptosis and inflammation in human umbilical vein endothelial cells by suppressing the NF-κB signaling pathway

The study investigated the expression of long noncoding RNA (lncRNA) MALAT1 in high glucose (HG)-induced human vascular endothelial cells (HUVECs) and the role of MALAT1 in the apoptosis of HG-induced HUVECs. The HUVECs were cultured and induced with 25 mmol/L HG. After that, the HUVECs were transfected with MALAT1 siRNA. The expression levels of MALAT1 were detected with qPCR, whereas the expression levels of Bax, Bcl-2, cleaved-caspase-3, cleaved-caspase-9, p-65, and p-p65 were detected using Western blot. The roles of MALAT1 in cell activities, including apoptosis, were evaluated using the CCK-8 assay, TUNEL staining, and flow cytometry. The expression levels of inflammatory factors (TNF-α and IL-6) were measured using ELISA. The expression levels of MALAT1, TNF-α, and IL-6 in HUVECs were increased in the HG environment; however, when MALAT1 was silenced in the HUVECs, cell proliferation increased significantly, the expression levels of TNF-α, IL-6, Bax, cleaved-caspase-3, and cleaved-caspase-9 decreased, and the rate of apoptosis also decreased. Silencing MALAT1 inhibited the expression of p-p65 in HG-induced HUVECs. In conclusion, our study demonstrated that MALAT1 is upregulated in HG-induced HUVECs, and inhibition of MALAT1 inhibits HG-induced apoptosis and inflammation in HUVECs by suppression of the NF-κB signaling pathway.

Thiamine pyrophosphate diminishes nitric oxide synthesis in endothelial cells

Although thiamine pyrophosphate (TPP) is considered a protective agent for endothelial cells, it is still unknown if this is associated with nitric oxide (NO) synthesis. Our aim was to evaluate the synthesis of NO in endothelial cells incubated with TPP and high glucose concentrations. Endothelial cells from the umbilical cord vein from newborns (n = 20), were incubated with 5, 15 or 30 mmol/L glucose, in absence or presence of 0.625 mg/ml of TPP. Our results showed a significant increase in cell proliferation (> 40%; P < 0.05), and cell viability (> 90%; P < 0.001) after 48 h in endothelial cells cultured with glucose plus TPP. Likewise, in the presence of glucose and TPP an important rise in the consumption of glucose by the endothelial cells was observed after 24 h (> 7%; P < 0.001) and 48 h (> 10%; P < 0.05). Additionally, the levels of lactate after incubation with glucose and TPP showed only slight variations after 48 h (P < 0.05). However, these changes were clearly different from those observed in the absence of TPP. Interestingly, we found that the changes mentioned were linked with reduced levels of nitrites both at 24 h (< 171 pmol/μg protein; P < 0.001), and 48 h (< 250 pmol/μg protein; P < 0.05), which was associated with a reduced expression of mRNA of eNOS in endothelial cells incubated with TPP and high glucose. In conclusion, the presence of TPP regulates the consumption of glucose and the synthesis of NO, which would explain its protective effect in the endothelium of diabetic patients.

Lactobacillus plantarum And Inulin: Therapeutic Agents to Enhance Cardiac Ob Receptor Expression and Suppress Cardiac Apoptosis in Type 2 Diabetic Rats

BACKGROUND

T2DM may cause increased levels of oxidative stress and cardiac apoptosis through elevated blood glucose. The present study investigated the effects of Lactobacillus plantarum (L. plantarum) as a probiotic strain and inulin as a prebiotic supplement on cardiac oxidative stress and apoptotic markers in type 2 diabetes mellitus (T2DM) rats.

METHODS

A high-fat diet and a low dose of streptozotocin were used to induce type 2 diabetes. The rats were divided into six groups which were supplemented with L. plantarum, inulin, or their combination for 8 weeks.

RESULTS

The results showed improved activity of cardiac antioxidant parameters including total antioxidant capacity (TAC), superoxide dismutase (SOD), and glutathione peroxidase (GPx) (P < 0.001, P < 0.01, and P < 0.01, respectively) and decreased level of cardiac malondialdehyde (MDA) concentration (P < 0.05). These changes were accompanied with increased protein expression of cardiac obesity receptor (Ob-R) (P = 0.05) and reduced apoptotic markers such as tumor necrosis factor-alpha (TNF-α), Fas ligand (FasL), and caspase proteins (P < 0.001, P = 0.003, and P < 0.01, respectively) in T2DM rats after concurrent L. plantarum and inulin supplementation. Moreover, a remarkable correlation of cardiac Ob-R and oxidative stress parameters with cardiac apoptotic markers was observed (P < 0.01).

CONCLUSION

The concurrent use of L. plantarum and inulin seems to be beneficial, as they can lead to decreased heart complications of T2DM via reducing cardiac apoptotic markers.

Astragaloside IV prevents high glucose‑induced cell apoptosis and inflammatory reactions through inhibition of the JNK pathway in human umbilical vein endothelial cells

Endothelial dysfunction is a key pathophysiological step in early stage diabetes mellitus (DM) macrovascular complications and is also crucial in the inflammatory mechanisms of macrovascular complications. However, there is currently no effective intervention to improve endothelial dysfunction associated with DM macrovascular complications. Astragaloside IV (AS-IV), which can be extracted from the traditional Chinese medicine Astragalus membranaceus, has potential therapeutic effects on DM and its complications. The present study evaluated the effect of AS-IV on high glucose-induced human umbilical vein endothelial cell (HUVEC) injury and its possible mechanism. The result indicated that AS-IV has a significant protective effect on high glucose-induced HUVEC injury. AS-IV could significantly promote cell proliferation, reduce apoptosis and decrease the protein and mRNA expression levels of tumor necrosis factor-α and interleukin-1β in HUVECs. Furthermore, AS-IV could decrease the expression of phosphorylated c-Jun NH₂-terminal kinase (JNK) phosphorylated apoptosis signal-regulating kinase 1, cytochrome c, cleaved-caspase-9, cleaved-caspase-3 and the relative ratio of B-cell lymphoma-2 associated X protein/B-cell lymphoma-2 in HUVECs. In conclusion, the present study demonstrated that AS-IV could suppress apoptosis and inflammatory reactions promoted by high glucose conditions in HUVECs by inhibiting the JNK signaling pathway. These findings suggest that AS-IV could inhibit the process of endothelial dysfunction in diabetic macrovascular complications.

Overexpression of hexokinase 2 reduces mitochondrial calcium overload in coronary endothelial cells of type 2 diabetic mice

Coronary microvascular rarefaction, due to endothelial cell (EC) dysfunction, is one of the causes of increased morbidity and mortality in diabetes. Coronary ECs in diabetes are more apoptotic due partly to mitochondrial calcium overload. This study was designed to investigate the role of hexokinase 2 (HK2, an endogenous inhibitor of voltage-dependent anion channel) in coronary endothelial dysfunction in type 2 diabetes. We used mouse coronary ECs (MCECs) isolated from type 2 diabetic mice and human coronary ECs (HCECs) from type 2 diabetic patients to examine protein levels and mitochondrial function. ECs were more apoptotic and capillary density was lower in the left ventricle of diabetic mice than the control. MCECs from diabetic mice exhibited significant increase in mitochondrial Ca²⁺ concentration ([Ca²⁺]_mito) compared with the control. Among several regulatory proteins for [Ca²⁺]_mito, hexokinase 1 (HK1) and HK2 were significantly lower in MCECs from diabetic mice than control MCECs. We also found that the level of HK2 ubiquitination was higher in MCECs from diabetic mice than in control MCECs. In line with the data from MCECs, HCECs from diabetic patients showed lower HK2 protein levels than HCECs from nondiabetic patients. High-glucose treatment, but not high-fat treatment, significantly decreased HK2 protein levels in MCECs. HK2 overexpression in MCECs of diabetic mice not only lowered the level of [Ca²⁺]_mito, but also reduced mitochondrial reactive oxygen species production toward the level seen in control MCECs. These data suggest that HK2 is a potential therapeutic target for coronary microvascular disease in diabetes by restoring mitochondrial function in coronary ECs.

Methylglyoxal-Induced Endothelial Cell Loss and Inflammation Contribute to the Development of Diabetic Cardiomyopathy

The mechanisms for the development of diabetic cardiomyopathy remain largely unknown. Methylglyoxal (MG) can accumulate and promote inflammation and vascular damage in diabetes. We examined if overexpression of the MG-metabolizing enzyme glyoxalase 1 (GLO1) in macrophages and the vasculature could reduce MG-induced inflammation and prevent ventricular dysfunction in diabetes. Hyperglycemia increased circulating inflammatory markers in wild-type (WT) but not in GLO1-overexpressing mice. Endothelial cell number was reduced in WT-diabetic hearts compared with nondiabetic controls, whereas GLO1 overexpression preserved capillary density. Neuregulin production, endothelial nitric oxide synthase dimerization, and Bcl-2 expression in endothelial cells was maintained in the hearts of GLO1-diabetic mice and corresponded to less myocardial cell death compared with the WT-diabetic group. Lower receptor for advanced glycation end products and tumor necrosis factor-α (TNF-α) levels were also observed in GLO1-diabetic versus WT-diabetic mice. Over a period of 8 weeks of hyperglycemia, GLO1 overexpression delayed and limited the loss of cardiac function. In vitro, MG and TNF-α were shown to synergize in promoting endothelial cell death, which was associated with increased angiopoietin 2 expression and reduced Bcl-2 expression. These results suggest that MG in diabetes increases inflammation, leading to endothelial cell loss. This contributes to the development of diabetic cardiomyopathy and identifies MG-induced endothelial inflammation as a target for therapy.

Tribbles homolog 3 is induced by high glucose and associated with apoptosis in human endothelial cells

Tribbles homolog 3 (TRIB3) is an intracellular kinase-like molecule that modifies cellular survival and metabolism. The present study aimed to investigate the function of TRIB3 regulation in the process of high glucose-induced apoptosis in endothelial cells, with the aim of identifying a novel intervention target for the prevention and treatment of diabetes mellitus. Human umbilical vein endothelial cells (HUVECs) grown in medium with various concentrations of glucose (5.5, 10, 20, 30 and 40 mmol/l) were assessed for mRNA expression of TRIB1, TRIB2 and TRIB3 using reverse transcription quantitative polymerase chain reaction. In addition, protein expression of TRIB3 was examined using western blot analysis. Immunofluorescence staining was performed in order to determine the distribution and localization of TRIB3 in HUVECs. Furthermore, cells grown in normal (5.5 mmol/l) or high glucose (HG; 30 mmol/l) medium were subjected to TRIB3 inhibition through small interfering (si)RNA knockdown. These cells were then examined in order to determine whether TRIB3 upregulation was associated with endothelial cell apoptosis. HUVECs treated with 30 and 40 mmol/l glucose for 48 h and 72 h showed significantly lower survival rates compared with those treated with normal glucose levels. In addition, slight but not significant increases in TRIB1 and TRIB2 mRNA expression were observed in HUVECs incubated with various concentrations of glucose for different durations. By contrast, TRIB3 mRNA expression was increased 7.2-fold following incubation with HG. Western blot analysis revealed a 5.44-fold increase in TRIB3 protein levels in cells grown in HG medium for 24 h compared with those grown in normal medium. Immunostaining assays revealed a markedly higher and well-defined nucleolar fluorescence intensity for TRIB3 expression at 24 h in HG medium compared with that of the control group. Furthermore, the apoptotic rate of HG-treated TRIB3 siRNA-transfected HUVECs was significantly increased compared with that of those transfected with control siRNA In conclusion, the results of the present study suggested that TRIB3 was associated with high glucose-induced HUVECs apoptosis, which was attenuated following transfection with TRIB3 siRNA.

The endothelium in diabetic nephropathy

Diabetes is characterised by widespread endothelial cell dysfunction that underlies the development of both the micro- and macrovascular complications of the disease, including nephropathy, cardiomyopathy, and non-proliferative retinopathy. In the kidney, major changes are noted in glomerular endothelial cell structure in their fenestrations and glycocalyx. These changes, along with endothelial cell loss and capillary rarefaction in both the glomerulus and tubulointerstitium, lead to the progressive loss of glomerular filtration that render diabetes the most common cause of end-stage renal disease in much of the developed world. New treatments in diabetes that directly address the abnormal structure and function of the endothelial cell are desperately needed.

Nanofiber Microenvironment Effectively Restores Angiogenic Potential of Diabetic Endothelial Cells

Objective: The effect of chronic hyperglycemic exposure on endothelial cell (EC) phenotype, impaired wound neovascularization, and healing is not completely understood. The hypotheses are: 1) chronic exposure to diabetic conditions in vivo impairs the angiogenic potential of ECs and 2) this deficiency can be improved by an extracellular microenvironment of angiogenic peptide nanofibers. Approach: Angiogenic potential of microvascular ECs isolated from diabetic (db/db) and wild type (wt) mice was assessed by quantifying migration, proliferation, apoptosis, capillary morphogenesis, and vascular endothelial growth factor (VEGF) expression for cell cultures on Matrigel (Millipore, Billerica, MA) or nanofibers under normoglycemic conditions. The in vivo effects of nanofiber treatment on wound vascularization were determined using two mouse models of diabetic wound healing. Results: Diabetic ECs showed significant impairments in migration, VEGF expression, and capillary morphogenesis. The nanofiber microenvironment restored capillary morphogenesis and VEGF expression and significantly increased proliferation and decreased cell apoptosis of diabetic cells versus wt controls. In diabetic wounds, nanofibers significantly enhanced EC infiltration, neovascularization, and VEGF protein levels, as compared to saline treatment; this effect was observed even in MMP9 knockout mice with endothelial progenitor cell (EPC) deficiency. Innovation: The results suggest a novel approach for correcting diabetes-induced endothelial deficiencies via cell interactions with a nanofiber-based provisional matrix in the absence of external angiogenic stimuli. Conclusion: Impaired endothelial angiogenic potential can be restored by angiogenic cell stimulation in the nanofiber microenvironment; this suggests that nanofiber technology for diabetic wound healing and treatment of other diabetes-induced vascular deficiencies is promising.

Diabetes mellitus aggravates hemorrhagic transformation after ischemic stroke via mitochondrial defects leading to endothelial apoptosis

Diabetes is a crucial risk factor for stroke and is associated with increased frequency and poor prognosis. Although endothelial dysfunction is a known contributor of stroke, the underlying mechanisms have not been elucidated. The aim of this study was to elucidate the mechanism by which chronic hyperglycemia may contribute to the worsened prognosis following stroke, especially focusing on mitochondrial alterations. We examined the effect of hyperglycemia on hemorrhagic transformation at 24 hours after middle cerebral artery occlusion (MCAO) in streptozotocin (STZ) -induced diabetic mice. We also examined the effects of high-glucose exposure for 6 days on cell death, mitochondrial functions and morphology in human brain microvascular endothelial cells (HBMVECs) or human endothelial cells derived from induced pluripotent stem cells (iCell endothelial cells). Hyperglycemia aggravated hemorrhagic transformation, but not infarction following stroke. High-glucose exposure increased apoptosis, capase-3 activity, and release of apoptosis inducing factor (AIF) and cytochrome c in HBMVECs as well as affected mitochondrial functions (decreased cell proliferation, ATP contents, mitochondrial membrane potential, and increased matrix metalloproteinase (MMP)-9 activity, but not reactive oxygen species production). Furthermore, morphological aberration of mitochondria was observed in diabetic cells (a great deal of fragmentation, vacuolation, and cristae disruption). A similar phenomena were seen also in iCell endothelial cells. In conclusion, chronic hyperglycemia aggravated hemorrhagic transformation after stroke through mitochondrial dysfunction and morphological alteration, partially via MMP-9 activation, leading to caspase-dependent apoptosis of endothelial cells of diabetic mice. Mitochondria-targeting therapy may be a clinically innovative therapeutic strategy for diabetic complications in the future.

Insulin therapy improves islet functions by restoring pancreatic vasculature in high-fat diet-fed streptozotocin-diabetic rats

BACKGROUND

In a previous study, we showed early insulin therapy could improve β-cell function in type 2 diabetic patients. However, the molecular mechanism was not clear. In the present study, we addressed this question by analyzing the pancreatic microvasculature in diabetic rats after insulin treatment.

METHODS

Diabetes was induced in rats by a combination of low dose streptozotocin (STZ; 40 mg/kg) and feeding of a high-fat diet. After the induction of diabetes, rats were treated with neutral protamine Hagedorn insulin (NPH; 6–8 U/day, s.c.) for 3 weeks. Three days after the end of treatment, rats were subjected to an intraperitoneal glucose tolerance test (IPGTT). The pancreatic microvasculature and the amount and size of the islets were evaluated by immunohistochemistry. Western blot analysis was used to determine levels of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGF-R2) protein.

RESULTS

Treatment with NPH improved insulin secretion from β-cells during the IPGTT and increased pancreatic islet size. The density of the microvasculature in the pancreas was determined by quantification of CD31, a marker of endothelial cells. Insulin treatment increased CD31 protein levels, as well as the expression of VEGF and VEGFR2.

CONCLUSIONS

The results suggest that insulin treatment improves islet recovery by increasing angiogenesis in the pancreas. The mechanism is related to the induction of VEGF and VEGFR2 expression in diabetic rats.

GABA tea prevents cardiac fibrosis by attenuating TNF-alpha and Fas/FasL-mediated apoptosis in streptozotocin-induced diabetic rats

GABA tea is a tea product that contains a high level of gamma-aminobutyric acid (GABA). This study investigated the effects of GABA tea on the heart in a diabetic rat model. Male Wistar rats were injected with 55mg/kg streptozotocin (STZ) to induce diabetes for 2weeks and then orally given dosages of 4.55 and 45.5mg/kg/day GABA tea extract for 6weeks. The results revealed that fasting blood glucose levels returned to normal levels in GABA tea-treated diabetic rats, but not in the untreated diabetic rats. Additionally, GABA tea effectively inhibited cardiac fibrosis induced by STZ. Further experiments showed that the STZ-induced protein levels of tumor necrosis factor-alpha (TNF-alpha), Fas, activated caspase-8 and caspase-3 were significantly inhibited by the GABA tea treatment. Therefore, our data suggest that the inhibiting effect of GABA tea on STZ-induced cardiac fibrosis in diabetic rats may be mediated by reducing blood glucose and further attenuating TNF-alpha expression and/or Fas/Fas ligand (FasL)-mediated apoptosis. These findings will provide implications for the potential anti-diabetic properties of GABA tea.

High admission glucose levels increase Fas apoptosis and mortality in patients with acute ST-elevation myocardial infarction: a prospective cohort study

Background

The presence of diabetes and plasma glucose concentration on admission are associated with adverse outcomes after an acute myocardial infarction (AMI), as high glucose can induce vascular endothelial cell apoptosis. This study explored the relative associations among admission plasma glucose level, soluble Fas (sFas) concentration, and long-term survival in patients with acute ST-elevation myocardial infarction (STEMI).

Methods

This prospective cohort study include 83 patients with acute STEMI. Based on their admission plasma glucose levels (7.8 and 11.1 mmol/L as the limits for low and high levels, respectively), patients were allocated into one of three groups: normal glucose (n = 33), median glucose (n = 24), and high glucose (n = 26). The admission plasma level of sFas was measured with a sandwich enzyme-linked immunosorbent assay (ELISA). Patients were followed up for an average of 89 ± 20 months for all causes of death and cardiovascular death.

Results

sFas levels were significantly higher in the high glucose group compared to the normal glucose group (5.87 ± 1.70 mmol/L vs. 3.07 ± 0.93 mmol/L, respectively, P < 0.05). The sFas level was positively associated with the admission plasma glucose level. The correlation coefficient (R) was 0.747, and R² was 0.559. Mortality was significantly higher in the high glucose group compared to the normal glucose group (19.2% vs. 3.0%, respectively, P < 0.05).

Conclusions

In patients with acute STEMI, plasma glucose level was high on admission, and sFas apoptosis levels were increased. Long-term follow-up revealed that a high admission plasma glucose level was associated with higher mortality compared to a normal admission glucose level.

Multi-targeted mechanisms underlying the endothelial protective effects of the diabetic-safe sweetener erythritol

Diabetes is characterized by hyperglycemia and development of vascular pathology. Endothelial cell dysfunction is a starting point for pathogenesis of vascular complications in diabetes. We previously showed the polyol erythritol to be a hydroxyl radical scavenger preventing endothelial cell dysfunction onset in diabetic rats. To unravel mechanisms, other than scavenging of radicals, by which erythritol mediates this protective effect, we evaluated effects of erythritol in endothelial cells exposed to normal (7 mM) and high glucose (30 mM) or diabetic stressors (e.g. SIN-1) using targeted and transcriptomic approaches. This study demonstrates that erythritol (i.e. under non-diabetic conditions) has minimal effects on endothelial cells. However, under hyperglycemic conditions erythritol protected endothelial cells against cell death induced by diabetic stressors (i.e. high glucose and peroxynitrite). Also a number of harmful effects caused by high glucose, e.g. increased nitric oxide release, are reversed. Additionally, total transcriptome analysis indicated that biological processes which are differentially regulated due to high glucose are corrected by erythritol. We conclude that erythritol protects endothelial cells during high glucose conditions via effects on multiple targets. Overall, these data indicate a therapeutically important endothelial protective effect of erythritol under hyperglycemic conditions.

Glucose toxic effects on granulation tissue productive cells: the diabetics' impaired healing

Type 2 diabetes mellitus is a metabolic noncommunicable disease with an expanding pandemic magnitude. Diabetes predisposes to lower extremities ulceration and impairs the healing process leading to wound chronification. Diabetes also dismantles innate immunity favoring wound infection. Amputation is therefore acknowledged as one of the disease's complications. Hyperglycemia is the proximal detonator of systemic and local toxic effectors including proinflammation, acute-phase proteins elevation, and spillover of reactive oxygen and nitrogen species. Insulin axis deficiency weakens wounds' anabolism and predisposes to inflammation. The systemic accumulation of advanced glycation end-products irreversibly impairs the entire physiology from cells-to-organs. These factors in concert hamper fibroblasts and endothelial cells proliferation, migration, homing, secretion, and organization of a productive granulation tissue. Diabetic wound bed may turn chronically inflammed, procatabolic, and an additional source of circulating pro-inflammatory cytokines, establishing a self-perpetuating loop. Diabetic fibroblasts and endothelial cells may bear mitochondrial damages becoming prone to apoptosis, which impairs granulation tissue cellularity and perfusion. Endothelial progenitor cells recruitment and tubulogenesis are also impaired. Failure of wound reepithelialization remains a clinical challenge while it appears to be biologically multifactorial. Ulcer prevention by primary care surveillance, education, and attention programs is of outmost importance to reduce worldwide amputation figures.

High glucose mediates endothelial-to-chondrocyte transition in human aortic endothelial cells

Background

Vascular calcification is one of the common complications in diabetes mellitus. Many studies have shown that high glucose (HG) caused cardiovascular calcification, but its underlying mechanism is not fully understood. Recently, medial calcification has been most commonly described in the vessels of patients with diabetes. Chondrocytes were involved in the medial calcification. Recent studies have shown that the conversion into mesenchymal stem cells (MSCs) via the endothelial-to-mesenchymal transition (EndMT) could be triggered in chondrocytes. Our previous research has indicated that HG induced EndMT in human aortic endothelial cells (HAECs). Therefore, we addressed the question of whether HG-induced EndMT could be transitioned into MSCs and differentiated into chondrocytes.

Methods

HAECs were divided into three groups: a normal glucose (NG) group, HG group (30 mmol/L), and mannitol (5.5 mmol/L NG + 24.5 mmol/L) group. Pathological changes were investigated using fluorescence microscopy and electron microscopy. Immunofluorescence staining was performed to detect the co-expression of endothelial markers, such as CD31, and fibroblast markers, such as fibroblast-specific protein 1 (FSP-1). The expression of FSP-1 was detected by real time-PCR and western blots. Endothelial-derived MSCs were grown in MSC medium for one week. The expression of the MSCs markers STRO-1, CD44, CD10 and the chondrocyte marker SOX9 was detected by immunofluorescence staining and western blots. Chondrocyte expression was detected by alcian blue staining. Calcium deposits were analyzed by alizarin red staining.

Results

The incubation of HAECs exposed to HG resulted in a fibroblast-like phenotype. Double staining of the HAECs indicated a co-localization of CD31 and FSP-1. The expression of FSP-1 was significantly increased in the HG group, and the cells undergoing EndMT also expressed STRO-1, CD44 and SOX9 compared with the controls (P < 0.05). Additionally, alcian blue staining in the HG group was positive compared to the NG group. Consistent with the evaluation of SOX9 expression, calcium deposits analyzed by alizarin red staining were also enhanced by the HG treatment. Specifically, we showed that HG-induced EndMT is accompanied by the activation of the canonical Snail pathway.

Conclusions

Our study demonstrated that HG could induce endothelial cells transdifferentiation into chondrocyte-like cells via the EndMT, which is mediated in part by the activation of the Snail signaling pathway.

Effects of some anti-diabetic and cardioprotective agents on proliferation and apoptosis of human coronary artery endothelial cells

BACKGROUND

The leading cause of death for patients suffering from diabetes is macrovascular disease. Endothelial dysfunction is often observed in type 2 diabetic patients and it is considered to be an important early event in the pathogenesis of atherogenesis and cardiovascular disease. Many drugs are clinically applied to treat diabetic patients. However, little is known whether these agents directly interfere with endothelial cell proliferation and apoptosis. This study therefore aimed to investigate how anti-diabetic and cardioprotective agents affect human coronary artery endothelial cells (HCAECs).

METHODS

The effect of anti-diabetic and cardioprotective agents on HCAEC viability, proliferation and apoptosis was studied. Viability was assessed using Trypan blue exclusion; proliferation in 5 mM and 11 mM of glucose was analyzed using [3H]thymidine incorporation. Lipoapoptosis of the cells was investigated by determining caspase-3 activity and the subsequent DNA fragmentation after incubation with the free fatty acid palmitate, mimicking diabetic lipotoxicity.

RESULTS

Our data show that insulin, metformin, BLX-1002, and rosuvastatin improved HCAEC viability and they could also significantly increase cell proliferation in low glucose. The proliferative effect of insulin and BLX-1002 was also evident at 11 mM of glucose. In addition, insulin, metformin, BLX-1002, pioglitazone, and candesartan significantly decreased the caspase-3 activity and the subsequent DNA fragmentation evoked by palmitate, suggesting a protective effect of the drugs against lipoapoptosis.

CONCLUSION

Our results suggest that the anti-diabetic and cardioprotective agents mentioned above have direct and beneficial effects on endothelial cell viability, regeneration and apoptosis. This may add yet another valuable property to their therapeutic effect, increasing their clinical utility in type 2 diabetic patients in whom endothelial dysfunction is a prominent feature that adversely affect their survival.

Exendin-4 restores glucolipotoxicity-induced gene expression in human coronary artery endothelial cells

Exendin-4, a stable GLP-1 receptor agonist, has been shown to stimulate insulin secretion. It has also been shown to exert beneficial effects on endothelial function that are independent of its glycemic effects. The molecular mechanisms underlying the protective actions of exendin-4 against diabetic glucolipotoxicity in endothelial cells largely remain elusive. We have investigated the long-term in vitro effect of palmitate or high glucose (simulating the diabetic milieu) and the role of exendin-4 on gene expression in human coronary artery endothelial cells. Gene expression profiling in combination with Western blotting revealed that exendin-4 regulates expression of a number of genes involved in angiogenesis, inflammation and thrombogenesis under glucolipotoxic conditions. Our results indicate that exendin-4 may improve endothelial cell function in diabetes through regulating expression of the genes, whose expression was disrupted by glucolipotoxicity. As endothelial dysfunction appears to be an early indicator of vascular damage, and predicts both progression of atherosclerosis and incidence of cardiovascular events, exendin-4 and possibly other incretin-based strategies may confer additional cardiovascular benefit beyond improved glycemic control.

Dehydroepiandrosterone inhibits the activation and dysfunction of endothelial cells induced by high glucose concentration

Dehydroepiandrosterone (DHEA), an adrenal steroid, has a protective role against diabetes; however, its mechanisms of action are unknown. Here, we focus on the effect of DHEA on the activation of endothelial cells induced by a high concentration of glucose. Adhesion on U937 cells, expression of adhesion molecules, production of ROS and NO, expression of eNOS, and translocation of NF-κB were evaluated in human umbilical vein endothelial cells (HUVEC) treated with high concentrations of glucose, DHEA, or both. High concentrations of glucose (>20mM) induced an increase in adhesion, an increment in mainly E-selectin and PECAM-1 expression, as well as in ROS and NO production, eNOS expression, translocation of NF-κB, and degradation of its inhibitor IκB-α. DHEA abolished adhesion and the increase of E-selectin, ICAM-1, VCAM-1, and PECAM-1 induced by glucose. In addition, DHEA completely blocked oxidative stress and decreased translocation of NF-κB and the degradation of IκB-α induced by glucose. These results suggest that DHEA protects against the activation of endothelial cells induced by high concentrations of glucose, indicating that DHEA could be useful in the treatment of hyperglycemia and diabetes.

Hyperglycemia raises the threshold of levosimendan- but not milrinone-induced postconditioning in rat hearts

Background

The authors examined whether milrinone and levosimendan could exert cardiac postconditioning effects in rats under normoglycemia and hyperglycemia, and whether the effects could be mediated by mitochondrial permeability transition pore (mPTP).

Methods

Wistar rats underwent 30-min coronary artery occlusion followed by 2-h reperfusion. The rats received milrinone or levosimendan just before reperfusion under normoglycemic or hyperglycemic conditions with or without atractyloside, an mPTP opener.

Results

Under normoglycemia, both 30 μg/kg milrinone (29 ± 12%) and 10 μg/kg levosimendan (33 ± 13%) reduced infarct size compared with that in the control (58 ± 7%). Under hyperglycemia, milrinone (34 ± 13%) reduced infarct size at the same dose as under normoglycemia. In contrast, neither 10 nor 30 μg/kg levosimendan protected hyperglycemic hearts, and only 100 μg/kg levosimendan (32 ± 9%) reduced infarct size compared with that in the hyperglycemic control (58 ± 13%). All of these cardioprotective effects under normoglycemia and hyperglycemia are abolished by atractyloside.

Conclusion

Milrinone and levosimendan exert postconditioning effects via inhibition of mPTP opening. Hyperglycemia raises the threshold of levosimendan-induced postconditioning, while milrinone-induced postconditioning is not influenced by hyperglycemia.