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

It is well established that oxidative modification of low-density lipoprotein (LDL) plays a causal role in human atherogenesis and the risk of atherosclerosis is increased in patients with diabetes mellitus. To examine the influence of different agents which may influence LDL-glycation and oxidation, experiments including glycation with glucose, glucose 6-phosphate, metal chelators (EDTA) and antioxidants (BHT) were performed. The influence of time dependence on the glycation process and the alteration of the electrophoretic mobility of LDL under diverse glycation and/or oxidation conditions was also investigated. The formation of conjugated dienes and levels of lipid peroxides in these different LDL-modifications were estimated. The copper-induced oxidation of LDL in vitro was determined by measurement of thiobarbituric acid reactive substances (TBARS) and expressed as nmol MDA/mg of LDL protein. We found that glycated LDL is more prone to oxidation than native LDL. Using native LDL, the maximal oxidation effect was found to reach a value of 49.72 nmol MDA/mg protein after 8 h. The maximum oxidation of the 31 days, glycated LDL with glucose was 71.76 nmol MDA/mg protein amounting to 144.33% of the value found for native LDL. In the case of glucose 6-phosphate glycation, the maximum oxidation under the same conditions amounted to 173.77% of the value found for native LDL. To measure the extent of glycation, fluorescence of advanced glycation end products (AGEs) was determined (370 nm excitation and 440 nm emission). The most potent glycation agent was glucose 6-phosphate leading to the formation of very high amounts of AGEs. This process was promoted in the absence of EDTA, which prevents the oxidative cleavage of modified Amadori products (ketoamines) to AGEs. We therefore conclude that both processes, glycation and oxidation, result in the modification of LDL. The lower the glycation-rate (+/- EDTA) as measured by relative fluorescence units RFU (generation of AGEs), the lower the additional oxidation rate after glycation as measured by TBARS (generation of MDA equivalents). Glycation and/or oxidation change the electrophoretic mobility of LDL.
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PMID:Why is glycated LDL more sensitive to oxidation than native LDL? A comparative study. 1104 92

The principal metabolic effect of metformin-an oral antihyperglycaemic agent-is the improvement in the sensitivity of peripheral tissues and liver to insulin. This study examined the effect of metformin monotherapy on antioxidative defence system activity in erythrocytes and plasma in diabetic patients. We studied the effect of metformin treatment on the activities of Cu, Zn-superoxide dismutase (EC 1. 15. 1. 1.), catalase (EC 1. 11. 1. 6.) and glutathione peroxidase (EC 1. 11. 1. 9.) in relation to lipid peroxidation products and reduced glutathione level in plasma and erythrocytes. In this study we also examined erythrocytes' susceptibility to H2O2-induced oxidative stress during metformin therapy. Although metformin monotherapy ameliorated the imbalance between free radical-induced increase in lipid peroxidation (by reducing the MDA level in both erythrocytes and plasma) and decreased plasma and cellular antioxidant defences (by increasing the erythrocyte activities of Cu, Zn, SOD, catalase and GSH level) and decreased erythrocyte susceptibility to oxidative stress, it had negligible effect to scavenge Fe ion-induced free radical generation in a phospholipid-liposome system.
Diabetes Obes Metab 2000 Aug
PMID:Effect of four-week metformin treatment on plasma and erythrocyte antioxidative defense enzymes in newly diagnosed obese patients with type 2 diabetes. 1122 59

Simple and efficient freezing methods with maximal postthawing recovery form the basis of ideal cryopreservation. Taurine (2-amino ethanesulfonic acid), an end-product of sulphur amino acid metabolism, is one of the most abundant free amino acids in the body. The membrane stabilizing, free radical scavenging, and osmoregulatory roles of taurine have been well documented. We studied the effect of physiological and supra-physiological concentrations (0.3 and 3.0 mM) of taurine on islet cryopreservation. Islet viability on cryopreservation was significantly improved in both the taurine-treated groups (91.9 +/- 2.3% in 0.3 mM and 94.6 +/- 1.58% in 3.0 mM group, p < 0.05) compared with the controls (85.7 +/- 3.4%). Loss of peripheral islet cells was highly reduced in the taurine group, as examined under phase contrast and quantified by islet morphometric analysis (p < 0.05) using a digital image analysis system. Taurine-treated islets showed significant reduction in lipid peroxidation (0.905 and 0.848 nM MDA/microg protein for 0.3 and 3.0 mM taurine, respectively, p < 0.05) compared with control (1.307 nM MDA/microg protein) islets. In all, 500 islet equivalents (IE) of treated or control group islets were transplanted to BALB/c mice rendered diabetic with STZ. All animals showed a normal glucose clearance following a glucose load. Graft functionality was confirmed by normoglycemia (fasting plasma glucose: fpg < 150 mg/dl) after transplantation and reappearing hyperglycemia (fpg > 200 mg/dl) following removal of the graft. Suboptimal islet transplantation using 250 IE suggests that the grafted islet mass was inadequate for diabetes reversal. In addition, no significant differences were observed in the islet insulin content between the three groups following cryopreservation of the islets at -196 degrees C. Our studies indicate that taurine pretreatment and its continued presence during islet cryopreservation improves the postthawing viable recovery of islets.
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PMID:Islet cryopreservation: improved recovery following taurine pretreatment. 1143 70

The high level of glucose in blood for a long duration is the main cause of the development of retinopathy. So yearly screening of patients newly diagnosed with NIDDM diabetes is recommended because rare cases of treatable diabetic retinopathy have occurred early in one course of NIDDM diabetes. Hyperglycaemia leads to non-enzymatic glycosylation of proteins and HbA1C was found increased. Antioxidants such as GSH and SOD level is found decreased in retinopathy conditions due to the higher lipid peroxidation, which is evident from high MDA and DC values. So it can be clearly stated that increase in the free radical by hyperglycaemia, lipid peroxidation and advanced glycosylation endproducts along with decreased antioxidants are the causative agents for the development of retinopathy.
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PMID:Lipid peroxidation and diabetic retinopathy. 1148 66

Modification of low density lipoprotein (LDL) particles due to oxidation, glycation and binding of advanced glycation end-products (AGEs) or malondialdehyde (MDA, a final product of lipid peroxidation) is considered most important in the process of atherogenesis. Oxidatively modified LDL are distinguished by another receptor type, which was discovered on the surface of macrophages and was called the scavenger receptor. Uncontrolled intake of LDL converts macrophages to foam cells; their accumulation under the vascular endothelium is considered as the first stage of atherosclerosis. Oxidation of LDL is a complex process taking place in both the extra- and intracellular space. At the end of this oxidative process, modified LDL particles show chemotactic, cytotoxic and immunogenic properties. Oxidized LDL express a large number of epitopes and cause production of polyclonal autoantibodies against these products, especially against apoB100 modified by MDA and 4-hydroxynonenal. IgoxLDL (antibodies against oxidized LDL) can be demonstrated either directly in intimal lesions or as a component of circulating immune complexes. IgoxLDL do not form a homogeneous group but a varied mixture of antibodies-isoantibodies caused by HDL and LDL polymorphism, antibodies against the lipid phase of LDL and antibodies against modified apoB100 of the immunoglobulin class IgA or IgG. Antibodies against oxLDL were found in many diseases other than atherosclerosis such as diabetes mellitus, renovascular syndrome, uremia, rheumatic fever, morbus Bechtjerev or lupus erythematodes. Newborns have practically the same levels of IgoxLDL as their mothers; however, these values did not differ from those in the healthy population of non-pregnant women of the same age. The decrease in IgoxLDL titer was very slow and lasted many months; that is why this parameter cannot be considered suitable for describing the rapid changes during oxidative stress of the organism. Positive correlation of IgoxLDL with antiphospholipids and other antibodies was repeatedly demonstrated; their determination can thus be used as a marker for the description of total production of autoantibodies in various diseases. The changes and correlations of IgoxLDL, anti-beta-2-glycoprotein I IgG and antiphospholipid antibodies support the immunological link between thrombotic and atherosclerotic processes in the human body.
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PMID:Antibodies against oxidized LDL--theory and clinical use. 1152 41

Women with diabetes mellitus are at high risk of myocardial infarction (MI), and it is well recognized that smoking, hypertension, hyperlipidaemia and the diabetic state itself do not fully explain this increased risk. During the last decade, growing evidence has accumulated that the immune system, with oxidized low-density lipoprotein (LDL) as a key antigen, plays an important role in the development of atherosclerosis. The aim of the present study was to explore the association between the immune response, as measured by antibody titres to malondialdehyde-treated LDL (MDA-LDL) and levels of C-reactive protein (CRP; a marker of inflammation), and diabetes mellitus and MI in women. Women (35-64 years) with diabetes (n=18) and non-diabetic women (n=46) who had been treated in hospital for MI were compared with diabetic women without MI (n=35) and healthy controls (n=70). Blood samples were collected after an overnight fast. CRP was determined with a highly sensitive immuno-enzymometric assay. IgM and IgG antibodies against MDA-LDL were analysed with a solid-phase ELISA technique. Women with diabetes but without previous MI were more similar to women with previous MI (both with and without diabetes) than to the healthy controls. Compared with healthy women, the women with diabetes and/or MI had higher IgG (P<0.05) and lower IgM (P=0.006) antibody titres against oxidized LDL and higher CRP levels (P<0.001), associations that were independent of other cardiovascular risk factors. These findings might indicate a differentiated immune response against modified LDL, more pronounced inflammation and a more aggressive atherosclerotic process in women with diabetes.
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PMID:Autoantibodies against oxidized low-density lipoprotein and C-reactive protein are associated with diabetes and myocardial infarction in women. 1167 58

Insulin resistance syndrome (IRS) is a cluster of prevalent conditions including glucose intolerance, hypertension and dyslipidemia, which commonly predispose to cardiovascular disease. However, the mechanism by which IRS is related with cardiovascular disease is not yet settled. Recently, it has been hypothesized that atherosclerosis is an inflammatory disease and that an increase in oxidative stress plays a key role in causing endothelial dysfunction associated with atherosclerosis. There has been, however, no study directly relating IRS with oxidative stress in human subjects. We measured various markers of oxidative stress among subjects who participated in a population-based epidemiological study performed in 1996. IRS was defined as non-diabetic subjects having more than two of three salient features of the syndrome (glucose intolerance, hypertriglyceridemia/low high density lipoprotein (HDL)-cholesterol and hypertension). The subjects with IRS (n=70) showed higher plasma malondialdehyde (MDA; 2.10+/-1.43 vs. 1.63+/-1.21 micromol/ml, P=0.009), homocysteine (16.32+/-8.34 vs. 13.06+/-6.49 micromol/l, P=0.002) and ceruloplasmin concentrations (29.80+/-5.28 vs. 27.39+/-5.10 mg/dl, P=0.002) than control subjects (n=196). Plasma MDA concentration was positively correlated with waist-to-hip ratio (r=0.124, P=0.044), and with plasma triglyceride (TG; r=0.163, P=0.008), ferritin (r=0.200, P=0.002) and homocysteine concentrations (r=0.136, P=0.032). These results suggest that increase in oxidative stress may contribute to the development of cardiovascular disease in IRS.
Diabetes Res Clin Pract 2001 Dec
PMID:Oxidative stress markers in Korean subjects with insulin resistance syndrome. 1173 6

Nonenzymatic glycation, i.e. binding of monosaccharides to amino groups of proteins, gives rise to complex components called "advanced glycation end-products" (AGEs), which alter protein structure and functions, and participate in diabetic long-term complications. Glycation and oxidative stress are closely linked, and are often referred to as "glycoxidation" processes. Experimental data support these interactions. a) All glycation steps generate oxygen free radicals, some of these steps being common with these of lipid peroxidation. b) AGEs bind to membrane receptors such as RAGE, and induce an oxidative stress and a pro-inflammatory status. c) Glycated proteins modulate cellular oxidative functions: glycated collagens induce an inappropriate oxidative response in PMNs. d) Products of lipid peroxidation (MDA) bind to proteins and amplify glycoxidation-induced damages. Glycoxydation intensity increases in diabetes mellitus, ageing, renal failure and other pathological states with oxidative stress. Therapies aiming at limiting glycoxidation take into account its oxidative part.
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PMID:[Advanced glycation end products (AGEs), free radicals and diabetes]. 1193 55

Nonenzymatic glycation of tissue and plasma proteins may stimulate the production of oxidant and carbonyl stress in diabetes. The aim of this study was to evaluate the effects of aminoguanidine (AG) on lipid peroxidation, protein oxidation and nitric oxide (NO) release in diabetic rat kidneys. After induction of diabetes with streptozotocin, female Wistar rats were divided into 2 groups. Group DAG (n=9) rats were given AG hydrogen carbonate (1 g/L) in drinking water and group D (n=8) was diabetic control rats given only tap water. Group H (n=8) was followed as healthy controls. At the end of an 8 week period, NO release, lipid and protein oxidation were determined in kidney tissues. NO release was significantly lower in diabetic rats compared with healthy controls (p<0.05). Lipid peroxidation was significantly high in group D (3.9 +/- 0.3 nmol MDA/g tissue) compared with the group DAG (2.6 0.1 nmol MDA/g tissue, p<0.01) and group H (2.4 +/- 0.2 nmol MDA/g tissue). Protein oxidation was significantly higher in diabetics than healthy controls (563.8 +/- 23.9, 655.8 +/- 7.2, 431.5 +/- 8.8 mmol carbonyl / g tissue for group DAG, D and H, respectively, p< 0.05). A positive correlation between albuminuria and thiobarbituric acid reactive substance (TBARS) levels (r= 0.54,p<0.005) and carbonyl content (r=0.70, p<0.0005) in kidney homogenate were observed. Although AG treatment had no effect on NO release, it significantly decreased lipid peroxidation in diabetic rat cortices. Consequently increased lipid peroxidation -as well as- protein oxidation could be involved in the pathogenesis of diabetic albuminuria.
Int J Exp Diabetes Res
PMID:Effects of aminoguanidine on lipid and protein oxidation in diabetic rat kidneys. 1199 Dec

The role of oxidative stress in streptozotocin (STZ)-induced toxicity and its prevention by a xanthone glucoside, mangiferin was investigated. To induce diabetes mellitus, adult male Wistar rats were injected STZ intravenously at 55 mg/kg body weight. The effect of mangiferin (10 and 20 mg/kg, i.p., 28 days) was investigated in STZ-induced diabetic male rats. Insulin-treated rats (6 U/kg, i.p., 28 days) served as positive control. Diabetic rats given normal saline served as negative control. Normal rats that neither received STZ nor drugs served as normal control. On day 28, the diabetic rats showed significant increase in serum creatine phosphokinase (CPK) and total glycosylated haemoglobin. Kidney revealed tubular degeneration and decreased levels of superoxide dismutase (SOD) and catalase (CAT) with an elevation of malonaldehyde (MDA). Cardiac SOD, CAT and lipid peroxidation were significantly increased. Histopathological findings revealed cardiac hypertrophy with haemorrhages. Analysis of erythrocyte revealed significantly elevated levels of MDA with insignificant decrease in CAT and SOD. Repeated intraperitoneal injections of mangiferin (10 and 20 mg/kg) and insulin (6 U/kg) controlled STZ-induced lipid peroxidation and significantly protected the animals against cardiac as well as renal damage. From the study, it may be concluded that oxidative stress appears to play a major role in STZ-induced cardiac and renal toxicity as is evident from significant inhibition of antioxidant defence mechanism in renal tissue or a compensatory increase in antioxidant defence mechanism in cardiac tissue. Intraperitoneal administration of mangiferin exhibited significant decrease in glycosylated haemoglobin and CPK levels along with the amelioration of oxidative stress that was comparable to insulin treatment.
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PMID:Mangiferin protects the streptozotocin-induced oxidative damage to cardiac and renal tissues in rats. 1209 13


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