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1.
Twenty-five years ago, the discovery of endothelium-derived relaxing factor opened a door that revealed a new and exciting role for the endothelium in the regulation of blood flow and led to the discovery that nitric oxide (NO) multi-tasked as a novel cell-signalling molecule. During the next 25 years, our understanding of both the importance of the endothelium as well as NO has greatly expanded. No longer simply a barrier between the blood and vascular smooth muscle, the endothelium is now recognized as a complex tissue with heterogeneous properties. The endothelium is the source of not only NO but also numerous vasoactive molecules and signalling pathways, some of which are still not fully characterized such as the putative endothelium-derived relaxing factor. Dysfunction of the endothelium is a key risk factor for the development of macro- and microvascular disease and, by coincidence, the discovery that NO was generated in the endothelium corresponds approximately in time with the increased incidence of type 2 diabetes. Primarily linked to dietary and lifestyle changes, we are now facing a global pandemic of type 2 diabetes. Characterized by insulin resistance and hyperglycaemia, type 2 diabetes is increasingly being diagnosed in adolescents as well as children. Is there a link between dietary-related hyperglycaemic insults to the endothelium, blood flow changes, and the development of insulin resistance? This review explores the evidence for and against this hypothesis.  相似文献   

2.
Glucagon-like peptide-1 (GLP-1) is one of the incretins, a gut hormone secreted from L cells in the intestine in response to food intake. It has been proposed as a potential therapeutic target for the treatment of patients with type 2 diabetes. However, the direct effects of GLP-1 on vascular injury in diabetes are largely unknown. Since there is a growing body of evidence that advanced glycation end products (AGE) and their receptor RAGE axis plays an important role in vascular complications in diabetes, this study investigated whether and how GLP-1 blocked the deleterious effects of AGE on human umbilical vein endothelial cells (HUVEC). GLP-1 receptor (GLP-1R) was expressed in HUVEC. GLP-1 dose-dependently inhibited RAGE gene expression in HUVEC, which was blocked by small interfering RNAs raised against GLP-1R. An analogue of cyclic AMP also decreased RAGE mRNA level in HUVEC. Further, GLP-1 decreased reactive oxygen species generation and subsequently reduced vascular cell adhesion molecule-1 mRNA levels in AGE-exposed HUVEC. Our present study suggests that GLP-1 directly acts on HUVEC via GLP-1R and it could work as an anti-inflammatory agent against AGE by reducing RAGE expression via activation of cyclic AMP pathways.  相似文献   

3.
Increasing evidence from both clinical and experimental studies indicates that the insulin-releasing hormone, glucagon-like peptide-1 (GLP-1) may exert additional protective/reparative effects on the cardiovascular system. The aim of this study was to examine vasorelaxant effects of GLP-1(7-36)amide, three structurally-related peptides and a non-peptide GLP-1 agonist in rat aorta. Interestingly, all GLP-1 compounds, including the established GLP-1 receptor antagonist, exendin (9-39) caused concentration-dependent relaxation. Mechanistic studies employing hyperpolarising concentrations of potassium or glybenclamide revealed that these relaxant effects are mediated via specific activation of ATP-sensitive potassium channels. Further experiments using a specific membrane-permeable cyclic AMP (cAMP) antagonist, and demonstration of increased cAMP production in response to GLP-1 illustrated the critical importance of this pathway. These data significantly extend previous observations suggesting that GLP-1 may modulate vascular function, and indicate that this effect may be mediated by the GLP-1 receptor. However, further studies are required in order to establish whether GLP-1 related agents may confer additional cardiovascular benefits to diabetic patients.  相似文献   

4.
Liraglutide is a glucagon-like peptide-1 (GLP-1) mimetic used for the treatment of Type 2 diabetes. Similar to the actions of endogenous GLP-1, liraglutide potentiates the post-prandial release of insulin, inhibits glucagon release and increases satiety. Recent epidemiological studies and clinical trials have suggested that treatment with GLP-1 mimetics may also diminish the risk of cardiovascular disease in diabetic patients. The mechanism responsible for this effect has yet to be determined; however, one possibility is that they might do so by a direct effect on vascular endothelium. Since low grade inflammation of the endothelium is an early event in the pathogenesis of atherosclerotic cardiovascular disease (ASCVD), we determined the effects of liraglutide on inflammation in cultured human aortic endothelial cells (HAECs). Liraglutide reduced the inflammatory responses to TNFα and LPS stimulation, as evidenced by both reduced protein expression of the adhesion molecules VCAM-1 and E-Selectin, and THP-1 monocyte adhesion. This was found to result from increased cell Ca2+ and several molecules sensitive to Ca2+ with known anti inflammatory actions in endothelial cells, including CaMKKβ, CaMKI, AMPK, eNOS and CREB. Treatment of the cells with STO-609, a CaMKK inhibitor, diminished both the activation of AMPK, CaMKI and the inhibition of TNFα and LPS-induced monocyte adhesion by liraglutide. Likewise, expression of an shRNA against AMPK nullified the anti-inflammatory effects of liraglutide. The results indicate that liraglutide exerts a strong anti-inflammatory effect on HAECs. They also demonstrate that this is due to its ability to increase intracellular Ca2+ and activate CAMKKβ, which in turn activates AMPK.  相似文献   

5.
Xie YW  Ming DS  Xu HX  Dong H  But PP 《Life sciences》2000,67(15):1913-1918
Methanolic extract and two purified compounds (brazilin and hematoxylin) from Caesalpinia sappan were examined for their relaxant effects in isolated rat thoracic aorta. The methanolic extract significantly and dose-dependently relaxed the alpha1-receptor agonist phenylephrine-precontracted aortic rings, without affecting passive tension of these vessels. Removal of the vascular endothelium, inhibition of nitric oxide (NO) synthase with 0.1 mM Nomega-nitro-L-arginine and of cGMP biosynthesis with 10 microM methylene blue abolished the vasorelaxant effects of the herbal extract at doses up to 30 microg/ml. Similar vasorelaxant effects were observed with brazilin and hematoxylin. Therefore, these results suggest that brazilin and hematoxylin may be responsible for the vascular relaxant effects of C. sappan, via endogenous NO and subsequent cGMP formation. The vascular relaxant effects of the plant may contribute to its therapeutic actions.  相似文献   

6.
GLP-1 stimulates insulin secretion, suppresses glucagon secretion, delays gastric emptying, and inhibits small bowel motility, all actions contributing to the anti-diabetogenic peptide effect. Endothelial dysfunction is strongly associated with insulin resistance and type 2 diabetes mellitus and may cause the angiopathy typifying this debilitating disease. Therefore, interventions affecting both endothelial dysfunction and insulin resistance may prove useful in improving survival in type 2 diabetes patients. We investigated GLP-1's effect on endothelial function and insulin sensitivity (S(I)) in two groups: 1) 12 type 2 diabetes patients with stable coronary artery disease and 2) 10 healthy subjects with normal endothelial function and S(I). Subjects underwent infusion of recombinant GLP-1 or saline in a random crossover study. Endothelial function was measured by postischemic FMD of brachial artery, using ultrasonography. S(I) [in (10(-4) dl.kg(-1).min(-1))/(muU/ml)] was measured by hyperinsulinemic isoglycemic clamp technique. In type 2 diabetic subjects, GLP-1 infusion significantly increased relative changes in brachial artery diameter from baseline FMD(%) (3.1 +/- 0.6 vs. 6.6 +/- 1.0%, P < 0.05), with no significant effects on S(I) (4.5 +/- 0.8 vs. 5.2 +/- 0.9, P = NS). In healthy subjects, GLP-1 infusion affected neither FMD(%) (11.9 +/- 0.9 vs. 10.3 +/- 1.0%, P = NS) nor S(I) (14.8 +/- 1.8 vs. 11.6 +/- 2.0, P = NS). We conclude that GLP-1 improves endothelial dysfunction but not insulin resistance in type 2 diabetic patients with coronary heart disease. This beneficial vascular effect of GLP-1 adds yet another salutary property of the peptide useful in diabetes treatment.  相似文献   

7.
目的:观察胰高糖素样肽-1(GLP-1)对脐静脉内皮细胞(HUVECs)释放一氧化氮(NO)的影响,并探讨GLP-1受体及GLP-1(9-36)在其中的作用。方法:分别以GLP-1、艾塞那肽、GLP-1(9-36)、GLP-1+exendin(9-39)、GLP-1+西格列汀、GLP-1+西格列汀+exendin(9-39)孵育HUVECs,取培养上清以硝酸还原酶法检测NO浓度。结果:GLP-1剂量依赖性的增加HUVECs中NO释放,艾塞那肽和GLP-1(9-36)均可刺激NO释放,exendin(9-39)和西格列汀均可部分阻断GLP-1引起的NO释放。结论:GLP-1可能通过GLP-1受体及GLP-1(9-36)相关的途径刺激HUVECs NO释放,发挥直接的血管保护作用。  相似文献   

8.
Glucagon-like peptide-1 (GLP-1)-based therapy of type 2 diabetes is executed either by GLP-1 receptor agonists, which stimulate the GLP-1 receptors, or by dipeptidyl peptidase-4 (DPP-4) inhibitors, which prevent the inactivation of endogenous GLP-1 thereby increasing the concentration of endogenous active GLP-1. GLP-1 activates pancreatic receptors resulting in improved glycemia through glucose-dependent stimulation of insulin secretion and inhibition of glucagon secretion. There is also a potential beta cell preservation effect, as judged from rodent studies. GLP-1 receptors are additionally expressed in extrapancreatic tissue, having potential for the treatment to reduce body weight and to potentially have beneficial cardio- and endothelioprotective effects. Clinical trials in subjects with type 2 diabetes have shown that in periods of 12 weeks or more, these treatments reduce HbA1c by ≈ 0.8–1.1% from baseline levels of 7.7–8.5%, and they are efficient both as monotherapy and in combination therapy with metformin, sulfonylureas, thiazolidinediones or insulin. Furthermore, GLP-1 receptor agonists reduce body weight, whereas DPP-4 inhibitors are body weight neutral. The treatment is safe with very low risk for adverse events, including hypoglycaemia. GLP-1 based therapy is thus a novel and now well established therapy of type 2 diabetes, with a particular value in combination with metformin in patients who are inadequately controlled by metformin alone.  相似文献   

9.

Background

A distinctive feature of type 2 diabetes is inability of insulin-secreting β-cells to properly respond to elevated glucose eventually leading to β-cell failure. We have hypothesized that an abnormally increased NO production in the pancreatic islets might be an important factor in the pathogenesis of β-cell dysfunction.

Principal Findings

We show now that islets of type 2 spontaneous diabetes in GK rats display excessive NO generation associated with abnormal iNOS expression in insulin and glucagon cells, increased ncNOS activity, impaired glucose-stimulated insulin release, glucagon hypersecretion, and impaired glucose-induced glucagon suppression. Pharmacological blockade of islet NO production by the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) greatly improved hormone secretion from GK islets suggesting islet NOS activity being an important target to inactivate for amelioration of islet cell function. The incretin hormone GLP-1, which is used in clinical practice suppressed iNOS and ncNOS expression and activity with almost full restoration of insulin release and partial restoration of glucagon release. GLP-1 suppression of iNOS expression was reversed by PKA inhibition but unaffected by the proteasome inhibitor MG132. Injection of glucose plus GLP-1 in the diabetic rats showed that GLP-1 amplified the insulin response but induced a transient increase and then a poor depression of glucagon.

Conclusion

The results suggest that abnormally increased NO production within islet cells is a significant player in the pathogenesis of type 2 diabetes being counteracted by GLP-1 through PKA-dependent, nonproteasomal mechanisms.  相似文献   

10.
The available evidence suggests that about two-thirds of the insulin response to an oral glucose load is due to the potentiating effect of gut-derived incretin hormones. The strongest candidates for the incretin effect are glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). In patients with type 2 diabetes, however, the incretin effect is lost or greatly impaired. It is hypothesized that this loss explains an important part of the impaired insulin secretion in patients. Further analysis of the incretin effects in patients has revealed that the secretion of GIP is near normal, whereas the secretion of GLP-1 is decreased. On the other hand, the insulintropic effect of GLP-1 is preserved, whereas the effect of GIP is greatly reduced, mainly because of a complete loss of the normal GIP-induced potentiation of second-phase insulin secretion. These two features, therefore, explain the incretin defect of type 2 diabetes. Strong support for the hypothesis that the defect plays an important role in the insulin deficiency of patients is provided by the finding that administration of excess GLP-1 to patients may completely restore the glucose-induced insulin secretion as well as the beta-cells' sensitivity to glucose. Because of this, analogs of GLP-1 or GLP-1 receptor activations are currently being developed for diabetes treatment, so far with very promising results.  相似文献   

11.
Hyperglycemia in diabetes causes increased oxidative stress in the vascular endothelium with generation of free radicals such as superoxide. Peroxynitrite, a highly reactive species generated from superoxide and nitric oxide (NO), induces proinflammatory tyrosine nitration of intracellular proteins under such conditions. The female sex hormone estrogen appears to exert protective effects on the nondiabetic endothelium. However, several studies show reduced vascular protection in women with diabetes, suggesting alterations in estrogen signaling under high glucose. In this study, we examined the endothelial effects of estrogen under increasing glucose levels, focusing on nitrotyrosine and peroxynitrite. Human umbilical vein endothelial cells were incubated with normal (5.5 mM) or high (15.5 or 30.5 mM) glucose before addition of estradiol (E2, 1 or 10 nM). Selective NO synthase (NOS) inhibitors were used to determine the role of specific NOS isoforms. Addition of E2 significantly reduced high glucose-induced increase in peroxynitrite and consequently, nitrotyrosine. The superoxide levels were unchanged, suggesting effects on NO generation. Inhibition of neuronal NOS (nNOS) reduced high glucose-induced nitrotyrosine, demonstrating a critical role for this enzyme. E2 increased nNOS activity under normal glucose while decreasing it under high glucose as determined by its phosphorylation status. These data show that nNOS contributes to endothelial peroxynitrite and subsequent nitrotyrosine generation under high glucose, which can be attenuated by E2 through nNOS inhibition. The altered regulation of nNOS by E2 under high glucose is a potential therapeutic target in women with diabetes.  相似文献   

12.
Sitagliptin is a stable inhibitor of dipeptidyl peptidase-IV, a responsible enzyme that mainly inactivates glucagon-like peptide-1 (GLP-1), and now one of the widely used agents for the treatment of diabetes. However, effects of sitagliptin on vascular injury are largely unknown. Since advanced glycation end products (AGEs) and their receptor (RAGE) axis contribute to vascular damage in diabetes, we investigated here whether sitagliptin inhibits the AGE-RAGE-induced endothelial cell damage in vitro. Although effects of 10?pM GLP-1 or 0.5?μM sitagliptin monotherapy on RAGE gene and protein expression were modest, combination therapy completely blocked the AGE-induced increase in RAGE mRNA and protein levels in human umbilical vein endothelial cells (HUVEC). AGEs induced reactive oxygen species (ROS) generation and reduced endothelial nitric oxide synthase (eNOS) mRNA level in HUVEC, both of which were also completely blocked by the treatment with 10?pM GLP-1 and 0.5?μM sitagliptin, but not with GLP-1 or sitagliptin monotherapy. Further, anti-RAGE antibody restored the decrease in eNOS mRNA level in AGE-exposed HUVEC. The present study suggests that sitagliptin augments the effects of GLP-1 on eNOS mRNA level in AGE-exposed HUVEC by suppressing RAGE expression and subsequent ROS generation. Sitagliptin may work as a vasoprotecitve agent in diabetes by blocking the AGE-RAGE axis.  相似文献   

13.
胰升血糖素样肽-1及其受体与 2 型糖尿病的治疗   总被引:1,自引:0,他引:1  
胰岛素对治疗 2 型糖尿病有一定效果,但长期使用会引起低血糖反应;双胍类药物降糖疗效显著,但会引起消化道不良反应 . 因此,寻找一种安全有效的药物是 2 型糖尿病治疗的当务之急 . 胰升血糖素样肽-1 作为一种胰岛素分泌促进剂和胰岛素增敏剂越来越受人们的关注,将它用于治疗糖尿病不会产生低血糖,对 1 型和 2 型糖尿病都有疗效 . 讨论胰升血糖素样肽-1及其受体的最新研究状况 .  相似文献   

14.
Sodium nitroprusside (SNP) is an endothelium-independent relaxant agent and its effect is attributed to its direct action on the vascular smooth muscle (VSM). Endothelium modulates the vascular tone through the release of vasoactive agents, such as NO. The aim of this study was to investigate the contribution of the endothelium on SNP vasorelaxation, NO release and Ca2+ mobilization. Vascular reactivity experiments showed that endothelium potentiates the SNP-relaxation in rat aortic rings and this effect was abolished by l-NAME. SNP-relaxation in intact endothelium aorta was inhibited by NOS inhibitors for the constitutive isoforms (cNOS). Furthermore, endogenous NO is involved on the SNP-effect and this endogenous NO is released by cNOS. Moreover, Ca2+ mobilization study shows that l-NAME inhibited the reduction of Ca2+-concentration in VSM cells and reduced the increase in Ca2+-concentration in endothelial cells induced by SNP. This enhancement in Ca2+-concentration in the endothelial cells is due to a voltage-dependent Ca2+ channels activation. The present findings indicate that the relaxation and [Ca2+]i decrease induced by SNP in VSM cells is potentiated by endothelial production of NO by cNOS-activation in rat aorta.  相似文献   

15.
Gastric inhibitory polypeptide: the neglected incretin revisited   总被引:6,自引:0,他引:6  
After the ingestion of fat- and glucose-rich meals, gut hormones are secreted into the circulation in order to stimulate insulin secretion. This so-called "incretin effect" is primarily conferred by Glucagon-like peptide 1 (GLP-1) and Gastric Inhibitory Polypeptide (GIP). In contrast to GLP-1, GIP has lost most of its insulinotropic effect in type 2 diabetic patients. In addition to its main physiological role in the regulation of endocrine pancreatic secretion, GIP exerts various peripheral effects on adipose tissue and lipid metabolism, thereby leading to increased lipid deposition in the postprandial state. In some animal models, an influence on gastrointestinal functions has been described. However, such effects do not seem to play an important role in humans. During the last years, the major line of research has focussed on GLP-1, due to its promising potential for the treatment of type 2 diabetes mellitus. However, the physiological importance of GIP in the regulation of insulin secretion has been shown to even exceed that of GLP-1. Furthermore, work from various groups has provided evidence that GIP contributes to the pathogenesis of type 2 diabetes to a considerable degree. Recent data with modified GIP analogues further suggested a possibility of therapeutic use in the treatment of type 2 diabetes. Thus, it seems worthwhile to refocus on this important and-sometimes-neglected incretin hormone. The present work aims to review the physiological functions of GIP, to characterize its role in the pathogenesis of type 2 diabetes, and to discuss possible clinical applications and future perspectives in the light of new findings.  相似文献   

16.
Glucagon-like peptide 1 (GLP-1) is an intestine-derived insulinotropic hormone that stimulates glucose-dependent insulin production and secretion from pancreatic beta-cells. Other recognized actions of GLP-1 are to suppress glucagon secretion and hepatic glucose output, delay gastric emptying, reduce food intake, and promote glucose disposal in peripheral tissues. All of these actions are potentially beneficial for the treatment of type 2 diabetes mellitus. Several GLP-1 agonists are in clinical trials for the treatment of diabetes. More recently, GLP-1 agonists have been shown to stimulate the growth and differentiation of pancreatic beta-cells, as well as to exert cytoprotective, antiapoptotic effects on beta-cells. Recent evidence indicates that GLP-1 agonists act on receptors on pancreas-derived stem/progenitor cells to prompt their differentiation into beta-cells. These new findings suggest an approach to create beta-cells in vitro by expanding stem/progenitor cells and then to convert them into beta-cells by treatment with GLP-1. Thus GLP-1 may be a means by which to create beta-cells ex vivo for transplantation into patients with insulinopenic type 1 diabetes and severe forms of type 2 diabetes.  相似文献   

17.
Glucagon-like peptide-1 (GLP-1) is a potent incretin hormone currently under investigation for use as a novel therapeutic agent in the treatment of type 2 diabetes. One of several therapeutically important biological actions of GLP-1 in type 2 diabetic subjects is ability to induce strong suppression of glucagon secretion. The glucagonostatic action of GLP-1 results from its interaction with a specific G-protein coupled receptor resulting in the activation of adenylate cyclase and an increase in cAMP generation. In the pancreatic alpha-cell, cAMP, via activation of protein kinase A, interacts with a plethora of signal transduction processes including ion-channel activity and exocytosis of the glucagon-containing granules. In this short review, we will focus on recent advances in our understanding on the cellular mechanisms proposed to underlie the glucagonotropic action of GLP-1 and attempt to incorporate this knowledge into a working model for the control of glucagon secretion. Studies on the effects of GLP-1 on glucagon secretion are relevant to the pathogenesis of type 2 diabetes due to the likely contribution of hyperglucagonemia to impaired glucose tolerance in type 2 diabetes.  相似文献   

18.
Vascular endothelium plays a crucial role in regulating blood flow and vascular tone. It can synthesize and release different relaxant factors including nitric oxide (NO). This article summarizes pharmacological properties of red wine polyphenol extracts (RWPC) with respect to endothelial NO. It is shown that RWPC produces endothelium-dependent relaxation as a result of enhanced NO synthesis rather than enhanced biological activity of NO or protection against breakdown by O2-. The mechanisms involve influx of Ca2+ and production of O2- within the endothelial cells. These results suggest that RWPC, by releasing endothelial NO, may have therapeutically relevant effects against cardiovascular diseases.  相似文献   

19.
The purpose of this study was to analyse the influence of experimental diabetes on vascular response of rabbit carotid artery to acetylcholine (Ach). We compared the Ach-induced relaxant response of isolated arterial segments obtained from both control and diabetic animals. To assess the influence of the endothelium, this cell layer was mechanically removed in some of the arterial segments ("rubbed arteries") from each experimental group. Ach induced a concentration-related endothelium-mediated relaxation of carotid artery from control rabbits that was significantly higher with respect to that obtained in diabetic animals. Pre-treatment with N(G)-nitro-L-arginine (L-NA) induced a concentration-dependent inhibition of relaxant response to Ach, which was significantly higher in carotid arteries isolated from diabetic rabbits. Incubation of rubbed arteries with L-NA almost abolished the relaxant response to Ach in arterial segments from both control and diabetic animals. Indomethacin potentiated Ach-induced response of carotid arteries from control rabbits, without modifying that obtained in those from diabetic animals. Aminoguanidine did not significantly inhibit the relaxant action of Ach in arterial segments from either control or diabetic rabbits. These results suggest that diabetes impairs endothelial modulatory mechanisms of vascular response of rabbit carotid artery to Ach. This endothelial dysfunction is neither related with a lower release of nitric oxide (NO) or prostacyclin. Diabetes impairs the production of some arachidonic acid vasoconstrictor derivative. There has been observed an increased modulatory activity of NO, but this is not related with the expression of an inducible isoform of NO synthase.  相似文献   

20.
糖尿病目前已成为继心血管疾病和肿瘤之后的第三位主要非传染性疾病,其中90%为2型糖尿病患者。胰高血糖素样肽-1类似物(GLP-I类似物)作为一种新型的降糖药物,具有降低体重、降低收缩压、改善胰岛细胞功能,已成为2型糖尿病治疗的新热点。艾塞那肽和利拉鲁肽作为肠促胰素激素,与人体内天然GLP-1保持了高度同源性(97%)。近几年来受到人们广泛关注。本综述针对2型糖尿病患者早期使用胰岛素样受体激动剂艾塞那肽和利拉鲁肽的安全性和有效性进行评估。  相似文献   

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