Leukocyte-endothelial cell interaction is attenuated by low-intensity exercise training and vitamin C supplementation in diabetic rats (original) (raw)
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Diabetic Medicine, 2006
Background Endothelial dysfunction (ED) has been described in Type 2 diabetes (T2DM). We have described previously a diminution of flow-mediated arterial dilatation and, by implication, further ED in T2DM in response to postprandial lipaemia (PPL) at 4 h. This is possibly mediated by oxidative stress/alteration of the nitric oxide (NO) pathway. T2DM subjects tend to exhibit both exaggerated and prolonged PPL. We therefore studied the relationship of PPL to the duration of ED in T2DM subjects and oxidative stress with or without the antioxidant, vitamin C. Methods Twenty subjects with T2DM with moderate glycaemic control (mean HbA 1c 8.4%) were studied. After an overnight fast, all subjects consumed a standard fat meal. Endothelial function (EF), lipid profiles, and venous free radicals were measured in the fasting, peak lipaemic phase (4 h) and postprandially to 8 h. The study was repeated in a double-blinded manner with placebo, vitamin C (1 g) therapy for 2 days prior to re-testing and with the fat meal. Oxidative stress was assessed by lipid-derived free radicals in plasma, ex vivo by electron paramagnetic resonance spectroscopy (EPR) and by markers of lipid peroxidation (TBARS). Endothelial function was assessed by flow-mediated vasodilatation (FMD) of the brachial artery. Results There was a significant decrease in endothelial function in response to PPL from baseline (B) 1.3 ± 1.3% to 4 h 0.22 ± 1.1% (P < 0.05) and 8 h 0.7 ± 0.9% (P < 0.05) (mean ± SEM). The endothelial dysfunction seen was attenuated at each time point with vitamin C. Baseline EF with vitamin C changed from (fasting) 3.8 ± 0.9-2.8 ± 0.8 (at 4 h) and 2.9 ± 1.3 (at 8 h) in response to PPL. Vitamin C attenuated postprandial (PP) oxidative stress significantly only at the 4-h time point [301.1 ± 118 (B) to 224.7 ± 72 P < 0.05] and not at 8 h 301.1 ± 118 (B) to 260 ± 183 (P = NS). There were no changes with placebo treatment in any variable.
Diabetes/Metabolism Research and Reviews, 2003
Background Defective leukocyte-endothelial interactions are observed in experimental diabetes and may reduce the capacity to mount an adequate inflammatory response. The present study investigated the effect of ascorbic acid, an inhibitor of free radical and glycated protein formation as well as an aldose reductase inhibitor, on leukocyte-endothelial interaction in alloxan-diabetic rats.
Probucol restores the defective leukocyte–endothelial interaction in experimental diabetes
European Journal of Pharmacology, 2003
Defective leukocyte -endothelial interactions have been observed in experimental type 1 diabetes. One of the mechanisms involved in the late complications of diabetes mellitus is the formation of free radicals species. Antioxidant treatment has been demonstrated to have beneficial effects on the complications observed in this pathology. Using intravital microscopy to visualize venules of the internal spermatic fascia, we demonstrated that the defective leukocyte -endothelial interactions in alloxan-induced diabetic rats could be corrected by probucol treatment. The defects were quantitated by the number of leukocytes rolling along the venular endothelium, sticking to the venular wall after topical application of zymosan-activated plasma (10% -0.1 ml) or leukotriene B 4 (1 AM/0.1 ml) and migrated after the application of a local irritant stimulus (carrageenan, 100 Ag/0.1 ml). Leukocyte counts, erythrocyte velocity and venular shear rate, unaltered in diabetic rats, were not modified by this treatment. Reactive oxygen species formation by endothelial cells increased in diabetic preparations, and the reduced expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and P-selectin in cross-sections of the whole testis of the animals, were both restored by the antioxidant agent. Therefore, antioxidant treatment improves leukocyte -endothelial interaction in diabetic rats at least in part by restoring the expression of adhesion molecules in venules of diabetic rats. D
Journal of Clinical Investigation, 1998
We addressed the role of hyperglycemia in leukocyte-endothelium interaction under flow conditions by exposing human umbilical vein endothelial cells for 24 h to normal (5 mM), high concentration of glucose (30 mM), advanced glycosylation end product-albumin (100 g/ml), or hyperglycemic (174-316 mg/dl) sera from patients with diabetes and abnormal hemoglobin A 1c (8.1 Ϯ 1.4%). At the end of incubation endothelial cells were perfused with total leukocyte suspension in a parallel plate flow chamber under laminar flow (1.5 dyn/cm 2 ). Rolling and adherent cells were evaluated by digital image processing. Results showed that 30 mM glucose significantly ( P Ͻ 0.01) increased the number of adherent leukocytes to endothelial cells in respect to control (5 mM glucose; 151 Ϯ 19 versus 33 Ϯ 8 cells/mm 2 ). A similar response was induced by endothelial stimulation with IL-1  , here used as positive control (195 Ϯ 20 cells/mm 2 ). The number of rolling cells on endothelial surface was not affected by high glucose level. Stable adhesion of leukocytes to glucosetreated as well as to IL-1  -stimulated endothelial cells was preceded by short interaction of leukocytes with the endothelial surface. The distance travelled by leukocytes before arrest on 30 mM glucose, or on IL-1  -treated endothelial cells, was significantly ( P Ͻ 0.01) higher than that observed for leukocytes adhering on control endothelium (30 mM glucose: 76.7 Ϯ 3.5; IL1  : 69.7 Ϯ 4 versus 5 mM glucose: 21.5 Ϯ 5 m). Functional blocking of E-selectin, intercellular cell adhesion molecule-1, and vascular cell adhesion molecule-1 on endothelial cells with the corresponding mouse mAb significantly inhibited glucose-induced increase in leukocyte adhesion (67 Ϯ 16, 83 Ϯ 12, 62 Ϯ 8 versus 144 Ϯ 21 cells/ mm 2 ). Confocal fluorescence microscopy studies showed that 30 mM glucose induced an increase in endothelial surface expression of E-selectin, intercellular cell adhesion molecule-1, and vascular cell adhesion molecule-1. Electro-phoretic mobility shift assay of nuclear extracts of human umbilical vein endothelial cells (HUVEC) exposed for 1 h to 30 mM glucose revealed an intense NF-kB activation. Treatment of HUVEC exposed to high glucose with the NF-kB inhibitors pyrrolidinedithiocarbamate (100 M) and tosyl-phe-chloromethylketone (25 M) significantly reduced ( P Ͻ 0.05) leukocyte adhesion in respect to HUVEC treated with glucose alone. A significant ( P Ͻ 0.01) inhibitory effect on glucose-induced leukocyte adhesion was observed after blocking protein kinase C activity with staurosporine (5 nM). When HUVEC were treated with specific antisense oligodesoxynucleotides against PKC ␣ and PKC ⑀ isoforms before the addition of 30 mM glucose, a significant ( P Ͻ 0.05) reduction in the adhesion was also seen. Advanced glycosylation end product-albumin significantly increased the number of adhering leukocytes in respect to native albumin used as control (110 Ϯ 16 versus 66 Ϯ 7, P Ͻ 0.01). Sera from diabetic patients significantly ( P Ͻ 0.01) enhanced leukocyte adhesion as compared with controls, despite normal levels of IL-1  and TNF ␣ in these sera.
Clinical Science, 2002
Type II diabetes is characterized by increased oxidative stress, endothelial dysfunction and hypertension. We investigated whether short-term treatment with oral vitamin C reduces oxidative stress and improves endothelial function and blood pressure in subjects with Type II diabetes. Subjects (n = 35) received vitamin C (1.5g daily in three doses) or matching placebo for 3 weeks in a randomized, double-blind, parallel-group design. Plasma concentrations of 8-epi-prostaglandin F2α (8-epi-PGF2α), a non-enzymically derived oxidation product of arachidonic acid, were used as a marker of oxidative stress. Endothelial function was assessed by measuring forearm blood flow responses to brachial artery infusion of the endothelium-dependent vasodilator acetylcholine (with nitroprusside as an endothelium-independent control) and by the pulse wave responses to systemic albuterol (endothelium-dependent vasodilator) and glyceryl trinitrate (endothelium-independent vasodilator). Plasma concentrati...
American Journal of Physiology-Heart and Circulatory Physiology, 2005
Endothelial dysfunction is a hallmark of Type 2 diabetes related to hyperglycemia and oxidative stress. Nitric oxide-dependent vasodilator actions of insulin may augment glucose disposal. Thus endothelial dysfunction may worsen insulin resistance. Intra-arterial administration of vitamin C improves endothelial dysfunction in diabetes. In the present study, we investigated effects of high-dose oral vitamin C to alter endothelial dysfunction and insulin resistance in Type 2 diabetes. Plasma vitamin C levels in 109 diabetic subjects were lower than healthy (36 ± 2 μM) levels. Thirty-two diabetic subjects with low plasma vitamin C (<40 μM) were subsequently enrolled in a randomized, double-blind, placebo-controlled study of vitamin C (800 mg/day for 4 wk). Insulin sensitivity (determined by glucose clamp) and forearm blood flow in response to ACh, sodium nitroprusside (SNP), or insulin (determined by plethysmography) were assessed before and after 4 wk of treatment. In the placebo gr...
Diabetes-metabolism Research and Reviews, 2006
BackgroundThis study investigates the contribution of vitamin supplementation to the efficacy of oral antidiabetic therapy on the reversal of endothelial dysfunction in a model of type-2 diabetes in rat.This study investigates the contribution of vitamin supplementation to the efficacy of oral antidiabetic therapy on the reversal of endothelial dysfunction in a model of type-2 diabetes in rat.MethodsDiabetes was induced by streptozotocin injection to neonatal rats which were breastfed for 4 weeks, then fed 6 weeks with normal food or food supplemented with 2% vitamin E and 4% vitamin C. Some diabetic rats were treated with gliclazide for 6 weeks. Endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside (SNP) were recorded in thoracic aortic rings. Plasma insulin, HbA1c and antioxidant vitamins (A, C and E); plasma and aortic malondialdehyde (MDA) levels were determined.Diabetes was induced by streptozotocin injection to neonatal rats which were breastfed for 4 weeks, then fed 6 weeks with normal food or food supplemented with 2% vitamin E and 4% vitamin C. Some diabetic rats were treated with gliclazide for 6 weeks. Endothelium-dependent and -independent relaxations to acetylcholine and sodium nitroprusside (SNP) were recorded in thoracic aortic rings. Plasma insulin, HbA1c and antioxidant vitamins (A, C and E); plasma and aortic malondialdehyde (MDA) levels were determined.ResultsInduction of diabetes resulted in decreased body weight and increased blood glucose, plasma insulin and HbA1c levels compared to controls. Acetylcholine relaxation was impaired in diabetic aorta, while SNP relaxation remained unchanged. Aortic MDA level was significantly higher, while plasma vitamin levels were lower in diabetic rats. Diminished acetylcholine response, enhanced aortic MDA level and decreased plasma vitamin levels were all restored after gliclazide and/or vitamin therapy. However, vitamin supplementation in control rats significantly impaired acetylcholine relaxations and increased aortic MDA levels.Induction of diabetes resulted in decreased body weight and increased blood glucose, plasma insulin and HbA1c levels compared to controls. Acetylcholine relaxation was impaired in diabetic aorta, while SNP relaxation remained unchanged. Aortic MDA level was significantly higher, while plasma vitamin levels were lower in diabetic rats. Diminished acetylcholine response, enhanced aortic MDA level and decreased plasma vitamin levels were all restored after gliclazide and/or vitamin therapy. However, vitamin supplementation in control rats significantly impaired acetylcholine relaxations and increased aortic MDA levels.ConclusionsApparently, a selective endothelial dysfunction accompanies the imbalance in oxidant/antioxidant status in the type-2 diabetes model of rat and gliclazide and/or vitamin supplementation improves the impairment in diabetic vasculature. However, vitamin supplementation triggers oxidative stress in normal aortic tissue, thereby, leads to endothelial dysfunction; indicating that nutritional extra-supplementation of antioxidant vitamins isn't advisable for normal subjects, although it's beneficial in disease status. Copyright © 2005 John Wiley & Sons, Ltd.Apparently, a selective endothelial dysfunction accompanies the imbalance in oxidant/antioxidant status in the type-2 diabetes model of rat and gliclazide and/or vitamin supplementation improves the impairment in diabetic vasculature. However, vitamin supplementation triggers oxidative stress in normal aortic tissue, thereby, leads to endothelial dysfunction; indicating that nutritional extra-supplementation of antioxidant vitamins isn't advisable for normal subjects, although it's beneficial in disease status. Copyright © 2005 John Wiley & Sons, Ltd.
Mechanisms Underlying Endothelial Dysfunction in Diabetes Mellitus
Circulation Research, 2001
Incubation of endothelial cells in vitro with high concentrations of glucose activates protein kinase C (PKC) and increases nitric oxide synthase (NOS III) gene expression as well as superoxide production. The underlying mechanisms remain unknown. To address this issue in an in vivo model, diabetes was induced with streptozotocin in rats. Streptozotocin treatment led to endothelial dysfunction and increased vascular superoxide production, as assessed by lucigenin-and coelenterazine-derived chemiluminescence. The bioavailability of vascular nitric oxide (as measured by electron spin resonance) was reduced in diabetic aortas, although expression of endothelial NOS III (mRNA and protein) was markedly increased. NOS inhibition with N G -nitro-L-arginine increased superoxide levels in control vessels but reduced them in diabetic vessels, identifying NOS as a superoxide source. Similarly, we found an activation of the NADPH oxidase and a 7-fold increase in gp91 phox mRNA in diabetic vessels. In vitro PKC inhibition with chelerythrine reduced vascular superoxide in diabetic vessels, whereas it had no effect on superoxide levels in normal vessels. In vivo PKC inhibition with N-benzoyl-staurosporine did not affect glucose levels in diabetic rats but prevented NOS III gene upregulation and NOS-mediated superoxide production, thereby restoring vascular nitric oxide bioavailability and endothelial function. The reduction of superoxide in vitro by chelerythrine and the normalization of NOS III gene expression and reduction of superoxide in vivo by N-benzoyl-staurosporine point to a decisive role of PKC in mediating these phenomena and suggest a therapeutic potential of PKC inhibitors in the prevention or treatment of vascular complications of diabetes mellitus. The full text of this article is available at http://www.circresaha.org. (Circ Res. 2001; 88:e14-e22.)
F1000 - Post-publication peer review of the biomedical literature, 2015
Strategies to prevent diabetic microvascular angiopathy focus on the vascular endothelium. Because red blood cells (RBCs) are less deformable in diabetes, we explored an original concept linking decreased RBC deformability to RBC ascorbate and hyperglycemia. We characterized ascorbate concentrations from human and mouse RBCs and plasma, and showed an inverse relationship between RBC ascorbate concentrations and deformability, measured by osmotic fragility. RBCs from ascorbate deficient mice were osmotically sensitive, appeared as spherocytes, and had decreased β-spectrin. These aberrancies reversed with ascorbate repletion in vivo. Under physiologic conditions, only ascorbate's oxidation product dehydroascorbic acid (DHA), a substrate for facilitated glucose transporters, was transported into mouse and human RBCs, with immediate intracellular reduction to ascorbate. In vitro, glucose inhibited entry of physiologic concentrations of dehydroascorbic acid into mouse and human RBCs. In vivo, plasma glucose concentrations in normal and diabetic mice and humans were inversely related to respective RBC ascorbate concentrations, as was osmotic fragility. Human RBC β-spectrin declined as diabetes worsened. Taken together, hyperglycemia in diabetes produced lower RBC ascorbate with increased RBC rigidity, a candidate to drive microvascular angiopathy. Because glucose transporter expression, DHA transport, and its inhibition by glucose differed for mouse versus human RBCs, human experimentation is indicated.
Endothelial Dysfunction, Inflammation and Diabetes
Reviews in Endocrine and Metabolic Disorders, 2000
The endothelium of blood vessels not only provides a mechanical lining, it is a biologically active inner layer of the blood vessel which serves several important functions. It ensures the patency of the blood vessel so that adequate blood flow can be maintained. This is achieved through its relaxant effect on vascular smooth muscle and its inhibitory effect on platelets. The normal endothelium also prevents the accumulation of leucocytes and the occurrence of thrombosis on its surface. In addition, it also promotes fibrinolysis to aid in the dissolution of micro-thrombi which may form . Endothelial function deteriorates with age and in the presence of several other factors which include hyperglycemia (diabetes), obesity, hypercholesterolemia, hypertension, menopause and smoking. These factors constitute the major risk factors of atherosclerosis. In view of the protean functions of the endothelium described above, it should be clear why endothelial dysfunction would be associated with a pro-constrictor state of the blood vessel, a proaggregatory state of the platelets, a pro-inflammatory state with the accumulation of leucocytes on the endothelium, a pro-thrombotic and an anti-fibrinolytic state . It should also be clear why the factors causing endothelial dysfunction are also the major risk factors for atherosclerosis.