UMLS:C0011849 - FACTA Search

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Query: UMLS:C0011849 (diabetes)
277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Mechanisms underlying endothelial dysfunction in diabetes mellitus. 1115 81

Decreased availability of arginine and impaired production of NO (nitric oxide) have been implicated in the development of endothelial dysfunction. Citrulline formed by the NOS reaction is recycled to arginine by the citrulline-NO cycle, which is composed of NOS, argininosuccinate synthetase (AS), and argininosuccinate lyase. Therefore, we investigated the alterations of these enzymes in the aorta of streptozotocin (STZ)-induced diabetic rats. eNOS and AS mRNAs were increased by three- to fourfold 1-2 weeks after STZ treatment and decreased at 4 weeks. AL mRNA was weakly induced. Induction of eNOS and AS proteins was also observed. Cationic amino acid transporter (CAT)-1 mRNA remained little changed, and CAT-2 mRNA was not detected. The plasma nitrogen oxide levels were increased 1-2 weeks after STZ treatment and decreased at 4 weeks. Transforming growth factor-beta1 (TGF-beta1) mRNA in the aorta was also induced. TGF-beta1 induced eNOS and AS mRNAs in human umbilical vein endothelial cells but inhibited the proliferation of HUVEC. These results indicate that eNOS and AS are coinduced in the aorta in early stages of STZ-induced diabetic rats and that the induction is mediated by TGF-beta1. The results also suggest that TGF-beta1 works antiatherogenically at early stages of diabetes by increasing NO production, whereas prolonged elevation of TGF-beta1 functions atherogenically by inhibiting endothelial cell growth.
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PMID:Coinduction of endothelial nitric oxide synthase and arginine recycling enzymes in aorta of diabetic rats. 1138 98

This study assessed whether the in vivo production of nitric oxide (NO) in the penis is impaired in experimental diabetes and whether this phenomenon can be explained by abnormal levels of NO synthase isoenzymes and/or plasma androgens. Adult male Sprague-Dawley rats were injected with streptozotocin (STZ) (40 mg/kg, i.p.) or vehicle. One half of the STZ-treated animals received daily insulin replacement. Twelve weeks later, the animals were tested for mating behavior and erectile reflexes. They were then anesthetized with urethane (1 g/kg), and the NO levels in their corpora cavernosa were monitored electrochemically with porphyrin microsensors before and after electrostimulation of the cavernous nerve. The intracavernous pressure (ICP) was measured simultaneously. The diabetic animals had substantial impairment in the mating and erectile reflexes tests, decreased basal and stimulated NO levels in the corpora, and a reduced ICP response to cavernous nerve stimulation. Insulin replacement fully reversed the effects of diabetes on the mating reflexes, the basal NO signals, and the ICP responses to electrical field stimulation and partially restored the stimulated NO release. Neither diabetes nor diabetes with insulin treatment had significant effects on serum testosterone levels or NOS isoform (nNOS, eNOS, and iNOS) protein content in penile homogenates, indicating that the changes found in erectile function were independent of such variables. These results also suggest that the diabetes-induced reduction in corporeal NO levels could be mainly due to the lack of some essential cofactors for NOS activity rather than to changes in the amount of enzyme proteins.
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PMID:Changes in mating behavior, erectile function, and nitric oxide levels in penile corpora cavernosa in streptozotocin-diabetic rats. 1175 Dec 81

To assess whether diabetes alters the content and/or expression of neuroactive agents and protooncogenes in afferent neurons of the vagus nerve, the nodose ganglia of streptozotocin (STZ)-induced diabetic rats were studied at 8, 16, and 24 weeks after induction of diabetes. Neuronal nitric oxide synthase (nNOS), tyrosine hydroxylase (TH), the immediate early gene c-Jun, vasoactive intestinal peptide (VIP) and calcitonin gene related peptide (CGRP) content and expression were measured in nodose ganglia of control, diabetic, and diabetic+insulin-treated rats using immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The numbers of nNOS-immunoreactive (ir) neurons were increased in the nodose ganglion of diabetic compared to control rats at the 8- and 16-week time points. However, no change was noted in the nNOS mRNA content of the diabetic nodose ganglion at either time point. Moreover, no alterations in the numbers of vagal efferent NOS-containing neurons (labeled with NADPH-diaphorase histochemistry) were noted in the dorsal motor nucleus of the vagus (DMV) or the nucleus ambiguous (NA) of control, diabetic, and diabetic+insulin-treated rats at any time point. Neither the numbers of TH-ir neurons nor the content of TH mRNA was altered in the diabetic rats at the 8- and 16-week time points. However, 24 weeks of diabetes resulted in a reduction in the numbers of TH-ir neurons in the diabetic nodose ganglia when compared to control, an effect not seen in diabetic rats receiving insulin. The number of nodose ganglion neurons labeled for the protooncogene, c-Jun, was small yet slightly increased in the diabetic nodose ganglia at the 8-week time point and was reversed with insulin treatment. The increase in c-Jun-ir neurons was not found at 16 or 24 weeks of diabetes. VIP-ir and CGRP-ir were unchanged at any of the time points. These data show that diabetes affects the content of some, but not all, neuroactive agents in the nodose ganglion and may reflect a modest level of diabetes-induced damage and/or alterations in axonal transport in the vagus nerve.
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PMID:Streptozotocin-induced diabetes and the neurochemistry of vagal afferent neurons. 1203 29

The aim of the study was to investigate antioxidant (alpha-lipoic acid [LA]) and gamma-linolenic acid treatments in the prevention of changes in autonomic nerves induced in streptozotocin-diabetic rats. Autonomic nerves supplying the heart, penis, and gut were examined using immunohistochemical and biochemical techniques. LA and gamma-linolenic acid (present in evening primrose oil [EPO]) were administered as dietary supplements ( approximately 80 and 200 mg. kg(-1). day(-1), respectively). LA treatment prevented the diabetes-induced decrease of norepinephrine (NA) in the heart and of type I nitric oxide synthase (NOS-I) expression in erectile tissue of the penis but failed to prevent diabetes-induced changes in NA-, vasoactive intestinal polypeptide-, or calcitonin gene-related peptide-containing nerves supplying the ileum. LA partially prevented and EPO totally prevented the increase in NOS-I activity induced by diabetes in the ileum. EPO treatment failed to prevent any other diabetes-induced changes in the heart, penis, or ileum. These results demonstrate that, whereas LA treatment is more effective than EPO in preventing diabetes-induced changes in autonomic nerves, the effectiveness of LA treatment varies with the target organ studied. Diabetes-induced changes in nerves supplying the ileum are more resistant to treatment than those of the heart and penis.
Diabetes 2003 Jan
PMID:The effectiveness of treatments of diabetic autonomic neuropathy is not the same in autonomic nerves supplying different organs. 1250 7

Common vascular disease states including diabetes, hypertension and atherosclerosis are associated with endothelial dysfunction, characterised by reduced bioactivity of nitric oxide (NO). Loss of the vasculoprotective effects of NO contributes to disease progression, but the mechanisms underlying endothelial dysfunction remain unclear. Increased superoxide production in animal models of vascular disease contributes to reduced NO bioavailability, endothelial dysfunction and oxidative stress. In human blood vessels, the NAD(P)H oxidase system is the principal source of superoxide, and is functionally related to clinical risk factors and systemic endothelial dysfunction. Furthermore, the C242T polymorphism in the NAD(P)H oxidase p22phox subunit is associated with significantly reduced superoxide production in patients carrying the 242T allele, suggesting a role for genetic variation in modulating vascular superoxide production. In vessels from patients with diabetes mellitus, endothelial dysfunction, NAD(P)H oxidase activity and protein subunits are significantly increased compared with matched non-diabetic vessels. Furthermore, the vascular endothelium in diabetic vessels is a net source of superoxide rather than NO production, due to dysfunction of endothelial NO synthase (eNOS). This deficit is dependent on the eNOS cofactor, tetrahydrobiopterin, and is in part mediated by protein kinase C signalling. These studies suggest an important role for both the NAD(P)H oxidases and endothelial NOS in the increased vascular superoxide production and endothelial dysfunction in human vascular disease states.
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PMID:Mechanisms of superoxide production in human blood vessels: relationship to endothelial dysfunction, clinical and genetic risk factors. 1251 89

Matrix metalloproteinases (MMPs) are responsible for the remodelling of the uterine extracellular matrix during embryo implantation. Nitric oxide (NO) production is increased at the time when implantation begins. Abnormal tissue levels of MMPs are present in diabetes; elevated NO levels in tissues and an increased oxidative stress are also found. The present work evaluates the uterine MMP2 activity and levels during embryo implantation, as well as the influence of nitridergic compounds and reactive oxygen species (ROS) on the MMP2 enzymatic activity in a model of neonatal streptozotocin-induced diabetic rat. Metalloproteinase 2 activity and levels are increased in diabetic tissues compared with controls (P < 0.05 and P < 0.002 respectively). The uterine enzymatic activity in diabetic animals decreases in the presence of the NOS inhibitor NG-nitro-L-arginine methyl ester (P < 0.01) and is enhanced (P < 0.005) when a generating ROS system (xanthine/xanthine oxidase) is added to the incubating medium. It was also found that uterine superoxide dismutase activity is higher in diabetic rats than in control rats on the day of implantation (P < 0.001), suggesting a compensatory antioxidant ability. In conclusion, the results show that the uterine MMP2 activity, which is higher in diabetic animals than in control animals, is modulated positively by NO and ROS during embryo implantation in a model of streptozotocin-induced diabetic rats.
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PMID:Metalloproteinase 2 activity and modulation in uterus from neonatal streptozotocin-induced diabetic rats during embryo implantation. 1261 92

Coronary and valvular heart disease during diabetes mellitus (DM) are major contributors of morbidity and mortality in the diabetic population. Relatively little atention has been given to the study of heart valve nerve structures in different pathological processes. In this study we have demonstrated the presence of possible morphological alterations in vessels of the anterior cusp of the rat mitral valve during 8-12 weeks DM. A histochemical method was used for the detection of NADPH-diaphorase (NADPH-d), which is the indirect NO-synthase marker. Arterioles and fine capillaries were localized in the attachment zone of the anterior cusp. Perivascular nerve fibres were identified running in the tunica adventitia. A marked dilatation of the vessels was seen in diabetes in comparison with control samples. No NADPH-d positive nerve fibres were observed in the tunica adventitia. It can be presumed that metabolic changes in the vessel walls during DM reflect modified neurotransmission of NO by means of their excessive overproduction of NOS (endothelial--eNOS) in endothelial cells. (Fig. 6, Ref. 32.).
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PMID:Alterations of the vessel wall innervation during diabetes mellitus. 1269 74

Evidence implicates hyperglycemia-derived oxygen free radicals as mediators of diabetic complications. However, intervention studies with classic antioxidants, such as vitamin E, failed to demonstrate any beneficial effect. Recent studies demonstrate that a single hyperglycemia-induced process of overproduction of superoxide by the mitochondrial electron-transport chain seems to be the first and key event in the activation of all other pathways involved in the pathogenesis of diabetic complications. These include increased polyol pathway flux, increased advanced glycosylation end product formation, activation of protein kinase C, and increased hexosamine pathway flux. Superoxide overproduction is accompanied by increased nitric oxide generation, due to an endothelial NOS and inducible NOS uncoupled state, a phenomenon favoring the formation of the strong oxidant peroxynitrite, which in turn damages DNA. DNA damage is an obligatory stimulus for the activation of the nuclear enzyme poly(ADP-ribose) polymerase. Poly(ADP-ribose) polymerase activation in turn depletes the intracellular concentration of its substrate NAD(+), slowing the rate of glycolysis, electron transport, and ATP formation, and produces an ADP-ribosylation of the GAPDH. These processes result in acute endothelial dysfunction in diabetic blood vessels that, convincingly, also contributes to the development of diabetic complications. These new findings may explain why classic antioxidants, such as vitamin E, which work by scavenging already-formed toxic oxidation products, have failed to show beneficial effects on diabetic complications and may suggest new and attractive "causal" antioxidant therapy. New low-molecular mass compounds that act as SOD or catalase mimetics or L-propionyl-carnitine and lipoic acid, which work as intracellular superoxide scavengers, improving mitochondrial function and reducing DNA damage, may be good candidates for such a strategy, and preliminary studies support this hypothesis. This "causal" therapy would also be associated with other promising tools such as LY 333531, PJ34, and FP15, which block the protein kinase beta isoform, poly(ADP-ribose) polymerase, and peroxynitrite, respectively. While waiting for these focused tools, we may have other options: thiazolinediones, statins, ACE inhibitors, and angiotensin 1 inhibitors can reduce intracellular oxidative stress generation, and it has been suggested that many of their beneficial effects, even in diabetic patients, are due to this property.
Diabetes Care 2003 May
PMID:New insights on oxidative stress and diabetic complications may lead to a "causal" antioxidant therapy. 1271 23

Proliferative modification of vascular smooth muscle cell (vSMC) and impaired bioavailability of nitric oxide (NO) have both been proposed among the mechanisms linking diabetes and atherosclerosis. However, diabetes induced modifications in phenotype and nitric oxide synthase(s) (NOS) expression and activity in vSMC have not been fully characterized. In this study, cell morphology, proliferative response to serum, alpha-SMactin levels, eNOS expression and activity, cGMP intracellular content, and superoxide anion release were measured in cultures of vSMC obtained from aorta medial layer of ten diabetic (90% pancreatectomy, DR) and ten control (sham surgery, CR) rats. Vascular SMC from DR showed a less evident "hill and valley" culture morphology, increased growth response to serum, greater saturation density, and lower levels of alpha-SMactin. In the same cells, as compared to CR cells, eNOS mRNA levels and NOS activity were increased, while intracellular cGMP level was lower and superoxide anion production was significantly greater. These data indicate that chronic hyperglycemia might induce, in the vascular wall, an increased number of vSMC proliferative clones which persist in culture and are associated with increased eNOS expression and activity. However, upregulation of eNOS and increased NO synthesis occur in the presence of a marked concomitant increase of O(2-) production. Since NO bioavailability, as reflected by cGMP levels, was not increased in DR cells, it is tempting to hypothesize that the proliferative phenotype observed in DR cells is associated with a redox imbalance responsible quenching and/or trapping of NO, with the consequent loss of its biological activity.
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PMID:Phenotype modulation in cultures of vascular smooth muscle cells from diabetic rats: association with increased nitric oxide synthase expression and superoxide anion generation. 1281 32

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