Effects of glucose and insulin on cultured human microvascular endothelial cells

Wildland fire, air pollution and cardiovascular health: is it time to focus on the microvasculature as a risk assessment tool?

Climate change favors weather conditions conducive to wildland fires. The intensity and frequency of forest fires are increasing, and fire seasons are lengthening. Exposure of human populations to smoke emitted by these fires increases, thereby contributing to airborne pollution through the emission of gas and particulate matter (PM). The adverse health outcomes associated with wildland fire exposure represent an important burden on the economies and health systems of societies. Even though cardiovascular diseases (CVDs) are the main of cause of the global burden of diseases attributable to PM exposure, it remains difficult to show reliable associations between exposure to wildland fire smoke and cardiovascular disease risk in population-based studies. Optimal health requires a resilient and adaptable network of small blood vessels, namely, the microvasculature. Often alterations of this microvasculature precede the occurrence of adverse health outcomes, including CVD. Biomarkers of microvascular health could then represent possible markers for the early detection of poor cardiovascular outcomes. This review aims to synthesize the current literature to gauge whether assessing the microvasculature can better estimate the cardiovascular impact of wildland fires.

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.

The relationship of systemic markers of haemostasis with retinal blood vessel responses in cardiovascular disease and/or diabetes

Background Hypercoagulability is a leading factor in diabetes and cardiovascular disease. Retinal vessel responses to flickering light are an important tool for assessing ocular function. We hypothesised a significant relationship between systemic markers of haemostasis and retinal vessel function. Methods Intra-ocular pressure and retinal microcirculation function were measured in 116 patients with diabetes and/or cardiovascular disease using unstimulated and stimulated arterial and venous retinal vessel responses to flickering light. Haemostasis was evaluated by platelet microparticles, soluble P selectin, and five functional markers of fibrin clot formation and lysis, hyperglycaemia by HbA1c. Results Intra-ocular pressure was linked to the rates of clot formation (p = 0.006) and clot dissolution (p = 0.013) whilst central retinal vein equivalent was linked to HbA1c (p = 0.017). In the first of three flickering light cycles only, arterial baseline diameter fluctuation was linked to the lag time to clot formation (p = 0.017), whilst maximum venous dilatation was linked to HbA1c (p = 0.001) and clot density (p = 0.011). HbA1c was linked to venous dilatation amplitude (p = 0.003). There were no significant links between any ocular index and any platelet index. Conclusions In addition to glycaemia, several haemostasis measures, but no measures of platelet activity, are linked to ocular and retinal blood vessel indices in patients with diabetes and/or cardiovascular disease. These associations may have pathophysiological significance.

Activation of the sweet taste receptor, T1R3, by the artificial sweetener sucralose regulates the pulmonary endothelium

A hallmark of acute respiratory distress syndrome (ARDS) is pulmonary vascular permeability. In these settings, loss of barrier integrity is mediated by cell-contact disassembly and actin remodeling. Studies into molecular mechanisms responsible for improving microvascular barrier function are therefore vital in the development of therapeutic targets for reducing vascular permeability in ARDS. The sweet taste receptor T1R3 is a G protein-coupled receptor, activated following exposure to sweet molecules, to trigger a gustducin-dependent signal cascade. In recent years, extraoral locations for T1R3 have been identified; however, no studies have focused on T1R3 within the vasculature. We hypothesize that activation of T1R3, in the pulmonary vasculature, plays a role in regulating endothelial barrier function in settings of ARDS. Our study demonstrated expression of T1R3 within the pulmonary vasculature, with a drop in expression levels following exposure to barrier-disruptive agents. Exposure of lung microvascular endothelial cells to the intensely sweet molecule sucralose attenuated LPS- and thrombin-induced endothelial barrier dysfunction. Likewise, sucralose exposure attenuated bacteria-induced lung edema formation in vivo. Inhibition of sweet taste signaling, through zinc sulfate, T1R3, or G-protein siRNA, blunted the protective effects of sucralose on the endothelium. Sucralose significantly reduced LPS-induced increased expression or phosphorylation of the key signaling molecules Src, p21-activated kinase (PAK), myosin light chain-2 (MLC2), heat shock protein 27 (HSP27), and p110α phosphatidylinositol 3-kinase (p110αPI3K). Activation of T1R3 by sucralose protects the pulmonary endothelium from edemagenic agent-induced barrier disruption, potentially through abrogation of Src/PAK/p110αPI3K-mediated cell-contact disassembly and Src/MLC2/HSP27-mediated actin remodeling. Identification of sweet taste sensing in the pulmonary vasculature may represent a novel therapeutic target to protect the endothelium in settings of ARDS.

Therapeutic angiogenesis by implantation of a capillary structure constituted of human adipose tissue microvascular endothelial cells

OBJECTIVE

We previously reported a novel technology for the engineering of a capillary network using an optical lithographic technique. To apply this technology to the therapy of ischemic diseases, we tested human omental microvascular endothelial cells (HOMECs) as an autologous cell source and decellularized human amniotic membranes (DC-AMs) as a pathogen-free and low immunogenic transplantation scaffold.

METHODS AND RESULTS

Human umbilical vein endothelial cells were aligned on a patterned glass substrate and formed a capillary structure when transferred onto an amniotic membrane (AM). In contrast, HOMECs were scattered and did not form a capillary structure on AMs. Treatment of HOMECs with sphingosine 1-phosphate (S1P) inhibited HOMEC migration and enabled HOMEC formation of a capillary structure on AMs. Using quantitative RT-PCR and Western blot analyses, we demonstrated that the main S1P receptor in HOMECs is S1P(2), which is lacking in human umbilical vein endothelial cells, and that inhibition of cell migration by S1P is mediated through an S1P(2)-Rho-Rho-associated kinase signaling pathway. Implantation of capillaries engineered on DC-AMs into a hindlimb ischemic nude mouse model significantly increased blood perfusion compared with controls.

CONCLUSIONS

A capillary network consisting of HOMECs on DC-AMs can be engineered ex vivo using printing technology and S1P treatment. This method for regeneration of a capillary network may have therapeutic potential for ischemic diseases.

Subcellular characterization of glucose uptake in coronary endothelial cells

Despite all the evidence linking glucose toxicity to an increased risk of cardiovascular diseases, very little is known about the regulation of glucose uptake in endothelial cells. We have previously reported an asymmetric distribution of the GLUTs (1-5) and SGLT-1 in en face preparations of rat coronary artery endothelia [Gaudreault N., Scriven D.R., Moore E.D., 2004. Characterisation of glucose transporters in the intact coronary artery endothelium in rats: GLUT-2 upregulated by long-term hyperglycaemia. Diabetologia 47(12),2081-2092]. We assessed this time, through immunocytochemistry and wide field fluorescence microscopy coupled to deconvolution, the presence and subcellular distribution of glucose transporters in cultures of human coronary artery endothelial cells (HCAECs). HCAECs express GLUT-1 to 5 and SGLT-1, but their subcellular distribution lacks the luminal/abluminal asymmetry and the proximity to cell-to-cell junctions observed in intact endothelium. To determine the impact of the transporters' distribution on intracellular glucose accumulation, a fluorescent glucose analog (2-NBDG) was used in conjunction with confocal microscopy to monitor uptake in individual cells; the arteries were mounted in an arteriograph chamber with physiological flow rates. The uptake in both preparations was inhibited by cytochalasin-B and d-glucose and stimulated by insulin, but the distribution of the incorporated 2-NBDG mirrored that of the transporters. In HCAEC it was distributed throughout the cell and in the intact arterial endothelium it was restricted to the narrow cytosolic volume adjacent to the cell-to-cell junctions. We suggest that the latter subcellular organization and compartmentalization may facilitate transendothelial transport of glucose in intact coronary artery.

Microcirculatory changes following reperfusion insult in diabetic rat skeletal muscles

We investigated the microcirculatory changes of ischemia/reperfusion injury in the diabetic rat cremaster muscle as well as the therapeutic effect of insulin. Streptozotocin-induced diabetic rats were maintained hyperglycemic for up to 8 weeks or were treated with insulin in the diabetic period. The rat cremaster muscle was prepared as an island flap and subjected to 2-h clamp ischemia followed by 1-h reperfusion. In nonischemic conditions, effective concentrations for 50% response (EC50) of serial orders of arterioles to norepinephrine were higher in diabetic muscles. Ischemia/reperfusion insult significantly decreased the EC50 of arterioles in the normal group, but not in the diabetic group. Light microscopy showed that the diabetic cremasters had more collapsed capillaries and smooth muscle-disarranged arterioles. Insulin therapy showed significant improvement in the diabetes-caused reduction of perfused capillary density, but not in the contractility of the diabetic arterioles. These results indicate that diabetes mellitus may damage the skeletal muscle microvasculature irreversibly and make it less responsive to autonomic regulation. Insulin therapy can improve capillary perfusion, but not the microvascular reactivity of diabetic muscles.

Therapy-resistant hypertension associated with central obesity, insulin resistance, and large muscle fibre area

Obesity and an enhanced insulin response to oral glucose tolerance test are associated with therapy resistance in hypertension. In order to explore this association further we studied the insulin sensitivity of subjects with essential hypertension resistant to triple drug therapy (RH), with the euglycemic insulin clamp technique. Well controlled hypertensives, matched for age, gender and body mass index (BMI) served as controls. Male subjects (7 RH and 7 controls) were further investigated by biopsies of Musculus Vastus lateralis since structural conditions in skeletal muscles might have a role in the above association. Irrespective of pre-study drug therapy, therapy-resistant hypertensives had a lower insulin sensitivity index than controls (p < 0.05). In spite of the BMI-match waist/hip ratio (WHR) in the RH males tended to be higher (p < 0.07). Insulin clearance tended to be lower in RH subjects (p = 0.09). BMI correlated with a reduced muscular capillary density (r = -0.77, p < 0.01). The average cross-sectional muscle fibre area was larger in RH subjects (p < 0.05). The mean muscle fibre area correlated with basal serum insulin (r = 0.63; p < 0.05). Rarefaction of the muscular capillary bed appears to be related to obesity. Larger muscle fibres might be an effect of the growth factor properties of insulin and could possibly correspond to hypertrophy of smooth muscle in the resistance vessels. This factor might contribute to the association of hyperinsulinemia and hypertension and attenuate the response to antihypertensive therapy.