Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Diabetes produces dramatic changes in retinal microvasculature, triggering endothelial cell proliferation and microaneurysms. Capillaries become weakened, releasing blood into vitreal and retinal spaces. Photoreceptors become occluded and separated from the choriocapillaris, resulting in visual acuity decline, detachment and cell death. Several models have been developed that have proved useful for the study of this disease, resulting in a better understanding of the processes involved. Streptozotocin treatment affects the pancreatic beta cells, rapidly reducing them until insulin is no longer synthesized in sufficient amounts. The galactosemic model shifts metabolism away from glucose, increasing aldose reductase and retinal polyol metabolism. Finally, two weeks of cycled oxygen from high to low tension every 24 hours, followed by return to room air, triggers microangiogenesis in developing retinas. Use of these models, separately or in combination, as well as electroretinographic analysis, has begun to reveal the events taking place as diabetic retinopathy progresses. Endothelial cells become separated from pericytes as basement membranes thicken, and vascular endothelial growth factor increases, triggering their proliferation. Finally, early changes occurring within photoreceptors can now be studied.
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PMID:Experimental models and their use in studies of diabetic retinal microangiopathy. 950 73

Elevation of intracellular glucose within retinal vascular cells is believed to be an important causal factor in the development of diabetic retinopathy. The intracellular glucose concentration is regulated by both the rate of glucose metabolism and glucose transport. Because retinal hypoxia often precedes proliferative diabetic retinopathy, we have studied the regulation of the glucose transport system by hypoxia in cultured bovine retinal endothelial cells (BRECs). Because retinal ischemia is known to increase intracellular adenosine levels, which subsequently regulate hypoxia-inducible genes, such as vascular endothelial growth factor and erythropoietin, the role of adenosine and its receptor-mediated pathways has also been evaluated. Hypoxia (0.5% O2, 5% CO2, and 94.5% N2) stimulated GLUT1 mRNA expression in BRECs in a time-dependent manner with an 8.9 +/- 1.5-fold (P < 0.01) increase observed after 12 h. GLUT1 mRNA expression returned to baseline (1.4 +/- 0.3-fold of control) within 12 h after reinstitution of normoxia. N6-Cyclopentyl adenosine (adenosine A1 receptor agonist, Kd = 1 nmol/l) did not affect GLUT1 mRNA expression at concentrations up to 1 micromol/l, while 2-p-(2-carboxyethyl)-phenethyl-amino-5'-N-ethylcarboxamidoadenosine and 5'-(N-ethylcalboxamido)-adenosine (adenosine A2 receptor [A2R] agonists, Kd = 15 and 16 nmol/l, respectively) increased mRNA levels at concentrations as low as 10 nmol/l. Maximal stimulation was 2.3 +/- 0.2- and 2.1 +/- 0.2-fold, respectively (P < 0.01). The adenosine A2a receptor antagonist 8-(3-chlorostyryl)caffeine (CSC) (Kd = 100 nmol/l for A2R) inhibited hypoxia-stimulated GLUT1 mRNA expression by 40 +/- 8% at 100 nmo/l. Hypoxia upregulated GLUT1 protein expression by 3.0 +/- 0.3-fold after 12 h (P < 0.01), but this response was attenuated by CSC (P < 0.05). Hypoxia increased glucose transport activity by 2.1 +/- 0.3-fold (P < 0.001) after 12 h, a response inhibited 65% by CSC (P < 0.01). A protein kinase A (PKA) inhibitor (H89, 20 micromol/l) suppressed hypoxia-induced GLUT1 mRNA expression by 42 +/- 9% (P < 0.01). These data suggest that hypoxia in BRECs upregulates glucose transport activity through an increase of GLUT1 expression that is partially mediated by adenosine, A2R, and the cAMP-PKA pathway.
Diabetes 1998 Sep
PMID:Hypoxia upregulates glucose transport activity through an adenosine-mediated increase of GLUT1 expression in retinal capillary endothelial cells. 972 38

Blood-retinal barrier (BRB) breakdown is a hallmark of diabetic retinopathy, but the molecular changes that cause this pathology are unclear. Occludin is a transmembrane component of interendothelial tight junctions that may regulate permeability at the BRB. In this study, we examined the effects of vascular endothelial growth factor (VEGF) and diabetes on vascular occludin content and barrier function. Sprague-Dawley rats were made diabetic by intravenous streptozotocin injection, and age-matched animals served as controls. After 3 months, BRB permeability was quantified by intravenous injection of fluorescein isothiocyanate-bovine serum albumin (FITC-BSA), Mr 66 kDa, and 10-kDa rhodamine-dextran (R-D), followed by digital image analysis of retinal sections. Retinal fluorescence intensity for FITC-BSA increased 62% (P < or = 0.05), but R-D fluorescence did not change significantly. Occludin localization at interendothelial junctions was confirmed by immunofluorescence, and relative protein content was determined by immunoblotting of retinal homogenates. Retinal occludin content decreased approximately 35% (P < or = 0.03) in the diabetic versus the control animals, whereas the glucose transporter GLUT1 content was unchanged in rat retinas. Additionally, treatment of bovine retinal endothelial cells in culture with 0.12 nmol/l or 12 nmol/l VEGF for 6 h reduced occludin content 46 and 54%, respectively. These data show that diabetes selectively reduces retinal occludin protein expression and increases BRB permeability. Our findings suggest that the elevated VEGF in the vitreous of patients with diabetic retinopathy increases vascular permeability by downregulating occludin content. Decreased tight junction protein expression may be an important means by which diabetes causes increased vascular permeability and contributes to macular edema.
Diabetes 1998 Dec
PMID:Vascular permeability in experimental diabetes is associated with reduced endothelial occludin content: vascular endothelial growth factor decreases occludin in retinal endothelial cells. Penn State Retina Research Group. 983 30

Diabetes mellitus is characterized by microangiopathy and increased angiogenic response in various organs. Basic fibroblast growth factor (bFGF) as well as vascular endothelial growth factor (VEGF) are both angiogenic and are involved in vascular endothelial cell growth. The purpose of this study was to determine serum levels of bFGF and VEGF, in children and adolescents (youngsters) with type 1 diabetes mellitus, and correlate them with parameters reflecting the severity of the disease. Forty diabetic youngsters without clinical evidence of complications were compared with 30 healthy control subjects (mean age +/- SD, 14.3 +/- 3.6 and 13.8 +/- 3.6 y, respectively). Diabetes duration and metabolic control (expressed by glycosylated Hb) were (mean +/- SD) 6.2 +/- 3.8 y and 9.6 +/- 1.8%, respectively. bFGF and VEGF (pg/mL) were measured in serum samples by enzyme immunoassays, and both were not significantly different between the type 1 diabetes mellitus and the control group (p = 0.952 and p = 0.559, respectively). Restricting the analysis to the type 1 diabetes mellitus group, neither the duration nor the metabolic control of the disease showed any correlation with bFGF and VEGF serum levels, whereas a significantly positive correlation was found between the two examined angiogenic factors both in the diabetic (r = 0.3464, p = 0.025) and the control group (r = 0.4619, p = 0.0013). In conclusion, serum levels of bFGF and VEGF were not found to vary significantly in diabetic youngsters in relation to controls and had no correlation with the duration and metabolic control of the disease. Nevertheless, a positive correlation was found between these two angiogenic factors both in the type 1 diabetes mellitus and the control group.
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PMID:Serum levels of basic fibroblast growth factor and vascular endothelial growth factor in children and adolescents with type 1 diabetes mellitus. 985 20

Diabetic nephropathy often co-exists with other manifestations of microangiopathy, in particular retinopathy. Recent clinical evidence suggests that inhibition of the renin-angiotensin system in humans can delay the development and/or progression of diabetic nephropathy and perhaps also retinopathy. The benefits of this therapeutic strategy may in part be explained by inhibition of the nonhaemodynamic actions of angiotensin II (Ang II). The recognized nonhaemodynamic actions of Ang II include the augmented release of many growth factors. Ang II can stimulate the release of vascular endothelial growth factor (VEGF) from human vascular tissues. VEGF is a family of potent cytokines which act to induce angiogenesis and markedly increase microvascular permeability. VEGF is abundantly expressed in the renal glomerulus, specifically within the podocyte, where its function is unknown. VEGF is also expressed in the retina and increased retinal VEGF expression occurs in diabetes and has been implicated in the pathogenesis of diabetic retinopathy. This review considers the potential clinical significance of Ang II-induced VEGF expression, if any, in the pathogenesis of diabetic nephropathy and retinopathy.
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PMID:A potential role for angiotensin II-induced vascular endothelial growth factor expression in the pathogenesis of diabetic nephropathy? 993 Mar 79

Diabetes is a major risk factor for coronary and peripheral artery diseases. Although diabetic patients often present with advanced forms of these diseases, it is not known whether the compensatory mechanisms to vascular ischemia are affected in this condition. Accordingly, we sought to determine whether diabetes could: 1) impair the development of new collateral vessel formation in response to tissue ischemia and 2) inhibit cytokine-induced therapeutic neovascularization. Hindlimb ischemia was created by femoral artery ligation in nonobese diabetic mice (NOD mice, n = 20) and in control C57 mice (n = 20). Hindlimb perfusion was evaluated by serial laser Doppler studies after the surgery. In NOD mice, measurement of the Doppler flow ratio between the ischemic and the normal limb indicated that restoration of perfusion in the ischemic hindlimb was significantly impaired. At day 14 after surgery, Doppler flow ratio in the NOD mice was 0.49+/-0.04 versus 0.73+/-0.06 for the C57 mice (P< or =0.005). This impairment in blood flow recovery persisted throughout the duration of the study with Doppler flow ratio values at day 35 of 0.50+/-0.05 versus 0.90+/-0.07 in the NOD and C57 mice, respectively (P< or =0.001). CD31 immunostaining confirmed the laser Doppler data by showing a significant reduction in capillary density in the NOD mice at 35 days after surgery (302+/-4 capillaries/mm2 versus 782+/-78 in C57 mice (P< or =0.005). The reduction in neovascularization in the NOD mice was the result of a lower level of vascular endothelial growth factor (VEGF) in the ischemic tissues, as assessed by Northern blot, Western blot and immunohistochemistry. The central role of VEGF was confirmed by showing that normal levels of neovascularization (compared with C57) could be achieved in NOD mice that had been supplemented for this growth factor via intramuscular injection of an adenoviral vector encoding for VEGF. We conclude that 1) diabetes impairs endogenous neovascularization of ischemic tissues; 2) the impairment in new blood vessel formation results from reduced expression of VEGF; and 3) cytokine supplementation achieved by intramuscular adeno-VEGF gene transfer restores neovascularization in a mouse model of diabetes.
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PMID:Rescue of diabetes-related impairment of angiogenesis by intramuscular gene therapy with adeno-VEGF. 1002 94

Ovulation, recurring every reproductive cycle of the mammalian female and triggered by a surge of luteinizing hormone (LH) released from the pituitary is an essential prerequisite for fertilization and subsequent embryonic development. Here we shall review two of the biological responses leading to follicle rupture -- vascular changes and proteolysis. Naturally, our present knowledge is based mainly on work in a few species, such as the rat, the mouse and, to lesser extent the pig and monkeys and observations in the human. Therefore any generalizations to other mammals, should be considered as a working hypothesis yet to be confirmed. The LH surge stimulates, in the preovulatory follicles, a cascade of proteolytic enzymes, including plasminogen activator (PA), plasmin and matrix metalloproteinases (MMPs). These enzymes bring about the degradation of perifollicular matrix and, most notably, the decomposition of the meshwork of collagen fibers which provides the strength to follicular wall. Pharmacological blockage of any of these enzymes resulted in the reduction of ovulation rate. The increased ovarian proteolytic activity associated with ovulation is controlled by locally produced specific inhibitors, plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of metalloproteases-1 (TIMP-1). The increased synthesis of these two specific proteinase inhibitors in the theca of growing follicles ensures their development by protecting them from enzymes diffusing from ovulatory follicles. The stimulation of ovulation by the gonadotropin results in an increase in follicular blood flow, hyperemia, increase in vascular permeability and a marked increase in follicular volume. These vascular changes and the proteolytic activity are triggered either directly by LH or by local mediators and factors produced in response to the gonadotropic stimulus. These mediators allow the tight coordination of these two cascades culminating in the rupture of follicle wall. We shall review here, briefly, the various mediatory systems that have been implicated in follicle rupture. These include steroids, vascular endothelial growth factor (VEGF), cytokines, eicosanoids, platelet activating factor (PAF), nitric oxide and nitric oxide synthase (NO/NOS), kinins and oxygen radicals.
Exp Clin Endocrinol Diabetes 1999
PMID:Molecular aspects of mammalian ovulation. 1007 49

Although reports from Europe indicate a reduction in the incidence of diabetes-related visual loss, diabetic retinopathy continues to be the leading cause of blindness. One agent, vascular endothelial growth factor (VEGF), has been found to stimulate angiogenesis and may be the cause of diabetic neovascularization and visual loss. New research implies that the manipulation of the VEGF pathway may be able to prevent diabetic visual loss. Type I (insulin-dependent) and type II (non-insulin-dependent) diabetes mellitus are different disease processes. There have been few attempts in the past to differentiate the retinopathy associated with these two distinct disorders. Recent reports indicate that these disorders have different responses to ocular therapy. Thyroid orbitopathy combined with ocular hypertension can produce true glaucoma. Nevertheless, this requires a prolonged duration of orbitopathy and most patients who have this combination will improve and not develop permanent glaucomatous changes. Similarly, the majority of Graves' disease patients develop improved function over time; however, the psychologic sequelae continue after the disease process is in remission, which warrants further studies.
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PMID:New discoveries in diabetes- and thyroid-related eye disease. 1017 5

Vascular alterations of peripheral nerves occuring after mechanical injury or in metabolic disorders are well described. It is thought that vascular endothelial growth factor (VEGF), a potent growth factor for angiogenesis, also plays an important role for regeneration of nervous tissue. We used a rat model of type I diabetes (streptozotozin-induced) with sensory neuropathy and with chronic hyperglycemia over 12 weeks. A monoclonal antibody to VEGF was used for immunohistochemistry of sciatic nerves and dorsal root ganglia (DRG). Intense VEGF staining was detected in cell bodies and nerve fibers of animals with chronic diabetes. Healthy control groups expressed no or very little VEGF and animals treated with insulin to prevent neuropathy and severe hyperglycemia showed significantly lower immunostaining for VEGF. After application of nerve growth factor (NGF), which is known to improve axonal and Schwann cell regeneration, a markedly decreased expression of VEGF was seen in diabetic animals. In contrast, enhanced VEGF staining was noted in NGF-treated healthy controls of the same age and body weight as the diabetic rats. Similar findings were made in diabetic animals treated with both, insulin and NGF. We conclude that functional alteration of peripheral nerves causes up-regulation of VEGF in Schwann cells and neurons. With functional restitution of nervous tissue, i.e. under insulin and/or NGF treatment VEGF expression decreases significantly. Additionally, NGF may stimulate VEGF in normal controls. The production of VEGF may play a role in complete nerve regeneration and its regulation may reflect the functional state of peripheral nerves.
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PMID:Vascular endothelial growth factor expression in peripheral nerves and dorsal root ganglia in diabetic neuropathy in rats. 1021 80

Diabetes mellitus is a significant cause of visual morbidity worldwide. Progress continues in the identification of cellular elements involved in the pathogenesis of diabetic eye disease. Most notable is a greater elucidation of the role of vascular endothelial growth factor. Studies on the epidemiology and clinical course of diabetic eye disease provide a basis for examination, prognosis, and treatment of affected patients.
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PMID:Ocular manifestations of diabetes. 1038 38


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