Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011860 (type 2 diabetes)
 57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucose is the main physiological stimulus for insulin biosynthesis and secretion by pancreatic beta-cells. Glucose-6-phosphatase (G-6-Pase) catalyzes the dephosphorylation of glucose-6-phosphate to glucose, an opposite process to glucose utilization. G-6-Pase activity in pancreatic islets could therefore be an important factor in the control of glucose metabolism and, consequently, of glucose-dependent insulin secretion. While G-6-Pase activity has been shown to be present in pancreatic islets, the gene responsible for this activity has not been conclusively identified. A homolog of liver glucose-6-phosphatase (LG-6-Pase) specifically expressed in islets was described earlier; however, the authors could not demonstrate enzymatic activity for this protein. Here we present evidence that the previously identified islet-specific glucose-6-phosphatase-related protein (IGRP) is indeed the major islet glucose-6-phosphatase. IGRP overexpressed in insect cells possesses enzymatic activity comparable to the previously described G-6-Pase activity in islets. The K(m) and V(max) values determined using glucose-6-phosphate as the substrate were 0.45 mm and 32 nmol/mg/min by malachite green assay, and 0.29 mm and 77 nmol/mg/min by glucose oxidase/peroxidase coupling assay, respectively. High-throughput screening of a small molecule library led to the identification of an active compound that specifically inhibits IGRP enzymatic activity. Interestingly, this inhibitor did not affect LG-6-Pase activity, while conversely LG-6-Pase inhibitors did not affect IGRP activity. These data demonstrate that IGRP is likely the authentic islet-specific glucose-6-phosphatase catalytic subunit, and selective inhibitors to this molecule can be obtained. IGRP inhibitors may be an attractive new approach for the treatment of insulin secretion defects in type 2 diabetes.
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PMID:Enzymatic characterization of the pancreatic islet-specific glucose-6-phosphatase-related protein (IGRP). 1472 2

Troglitazone (TGZ) was the first glitazone used for the treatment of type II diabetes mellitus. TGZ undergoes an oxidative chroman ring-opening reaction to form a quinone product. Recently, cytochrome P450 (P450) was shown to be able to catalyze the formation of TGZ quinone. TGZ quinone was the major metabolite formed by dexamethasone-induced rat liver microsomes or myeloperoxidase (MPO) incubated with TGZ. The ultimate source for the quinone carbonyl oxygen atom of TGZ quinone was investigated using (18)O water in both enzyme reaction systems followed by liquid chromatography/tandem mass spectometry analysis of the TGZ quinone product. The resultant TGZ quinone formed by either liver microsomes or MPO contained a single atom of (18)O. The (18)O atom was determined to be the quinone carbonyl oxygen by collision-induced dissociation fragmentation of the (18)O-labeled TGZ quinone. The formation of TGZ quinone was inhibited approximately 90% by coincubation with ascorbic acid or cysteine in the MPO reaction system but only 10 to 20% in liver microsomes, which might reflect the difference in the mechanism by which TGZ quinone is formed by P450 and peroxidase. These results suggest that P450 catalyze an atypical reaction to form TGZ quinone, involving the incorporation of an oxygen from water into the quinone carbonyl position.
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PMID:Incorporation of an oxygen from water into troglitazone quinone by cytochrome P450 and myeloperoxidase. 1503 98

Increased oxidative stress and impaired anti-oxidant defense have been suggested as contributory factors for initiation and progression of complications in diabetes mellitus. Aging itself has been shown to be along with increased oxidative stress and lower anti-oxidant defense. We aimed at investigating oxidative stress and anti-oxidant enzymes in 61 elderly subjects. Fifteen healthy individuals (group 1, mean age 72.2 +/- 5.13), 13 glucose intolerant patients (group 2, mean age 71.7 +/- 4.9), 19 patients with type 2 diabetes mellitus (T2DM) without any complication (group 3, mean age 70.0 +/- 6.0), and 14 patients with T2DM with at least one complication (group 4, mean age 69.8 +/- 4.7) were included in the study. Whilst plasma levels for malondialdehyde (MDAP) and erythrocyte malondialdehyde (MDAE) were measured as markers of oxidative stress, activity of erythrocyte superoxide dismutase (SOD), glutathion peroxidase (GSH-Px), and catalase (CAT) were taken as markers of oxidative defense system. MDAP level was significantly elevated in group 4 (P = 0.001). MDAE was elevated in patients with T2DM, particularly in group 4, however, the difference between the groups was of borderline significance (P = 0.07). Whilst CAT was elevated in groups 3 and 4 compared to control subjects (P = 0.025 and 0.002, respectively), no difference was found for SOD between the groups. GSH-Px activity was found to be increased in groups 2, 3 and 4, it did not reach statistical significance (P = 0.106). There were significant correlations between CAT and MDAE (P < 0.0001, r = 0.056) and MDAP (P = 0.016, r = 0.306). These results suggest that there was an increased oxidative stress in elderly diabetics, however, this is not due to reduced erythrocyte antioxidant defense potential but, rather, increased free radical production possibly due to hyperglycemia.
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PMID:Oxidative stress and antioxidant status in elderly diabetes mellitus and glucose intolerance patients. 1538 45

An ELISA for urine microalbumin using microtiter plates has been developed. The assay uses polyclonal anti-human albumin antibody for coating the microtiter plates and the same antibody conjugated with horseradish peroxidase for detection. The assay sensitivity is 1.6 microg/ml. Results by this in-house ELISA show good correlation (r = 0.99) with those obtained by a commercial assay using the Behring BNII autoanalyzer. Within-day and between-day CVs are 10%. Reference values for microalbumin in 769 urine specimens from healthy Chinese subjects were higher in women than men and higher in subjects 50 yr than in those <50 yr of age. Elevated mean concentrations of urine microalbumin were observed in patients with type 2 diabetes and CVD. This in-house ELISA is simple, sensitive, precise, and especially suited for laboratories without expensive autoanalyzers.
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PMID:Microplate ELISA for urine microalbumin: reference values and results in patients with type 2 diabetes and cardiovascular disease. 1594 78

Diabetes mellitus is characterized by fasting hyperglycemia, with both type 1 and type 2 diabetes. Persons are also known to be prone to develop complications related to elevated blood glucose concentrations, including atherosclerosis, retinal damage, cataract, and neuropathy. Hyperglycemia may also result in increased production of the reactive oxygen species within numerous biochemical pathways that have the potential to initiate changes in endothelial function. This article demonstrates the presence of lipid peroxidation products in the red cell membranes of type 2 diabetic patients compared to the normal subjects. These membranes are more susceptible to exogenous oxidative stress than those of normal healthy individuals. Significantly higher activities of antioxidant enzymes, namely, serum peroxidase, superoxide dismutase (SOD), and catalase (CAT) were found in type 2 diabetic patients as compared to control. This study led us to conclude that elevated levels of glucose induce oxidative stress that is ultimately reflected by the increased malondialdehyde (MDA) levels in erythrocyte ghost membranes of diabetic patients. Hyperglycemia also induced an increase in antioxidant enzymes and a relationship seems to exist between diabetic complications and elevated levels of these enzymes. It is suggested that these antioxidant enzymes may be considered as markers for vascular injury.
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PMID:Lipid peroxidation and serum antioxidant enzymes in patients with type 2 diabetes mellitus. 1715 23

The possible contribution of early changes in lipid composition, function, and antioxidant status of abdominal adipose tissue (AAT) induced by a fructose-rich diet (FRD) to the development of insulin resistance (IR) and oxidative stress (OS) was studied. Wistar rats were fed with a commercial diet with (FRD) or without 10% fructose in the drinking water for 3 weeks. The glucose (G), triglyceride (TG), and insulin (I) plasma levels, and the activity of antioxidant enzymes, lyposoluble antioxidants, total glutathione (GSH), lipid peroxidation as TBARS, fatty acid (FA) composition of AAT-TG as well as their release by incubated pieces of AAT were measured. Rats fed with a FRD have significantly higher plasma levels of G, TG, and I. Their AAT showed a marked increase in content and ratios of saturated to monounsaturated and polyunsaturated FAs, TBARS, and catalase, GSH-transferase and GSH-reductase, together with a decrease in superoxide dismutase and GSH-peroxidase activity, and total GSH, alpha-tocopherol, beta-carotene and lycopene content. Incubated AAT from FRD released in vitro higher amount of free fatty acids (FFAs) with higher ratios of saturated to monounsaturated and polyunsaturated FAs. Our data suggest that FRD induced an early prooxidative state and metabolic dysfunction in AAT that would favor the overall development of IR and OS and further development of pancreatic beta-cell failure; therefore, its early control would represent an appropriate strategy to prevent alterations such as the development of type 2 diabetes.
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PMID:Abdominal adipose tissue: early metabolic dysfunction associated to insulin resistance and oxidative stress induced by an unbalanced diet. 1862 97

Adiponectin (APN) is present in human plasma as a low molecular weight (LMW), a middle molecular weight (MMW) and a high molecular weight form (HMW). As a support to determine properties such as anti-atherogenic or atherogenic effects, recent clinical studies suppose to determine the ratio of each APN multimer to total APN but not the absolute plasma concentration of APN. In the present study, the correlation of APN and its multimers with myeloperoxidase (MPO), an enzyme with pro-inflammatory properties, was examined in patients with type 2 diabetes mellitus. MPO and APN serum levels were assessed in 49 patients with type 2 diabetes mellitus at the beginning and at the end of an anti-diabetic treatment. After treatment a significant increase in the ratio of HMW to total APN (from 0.43+/-0.16 to 0.59+/-0.14, p<0.05) was found. Before treatment, HMW-APN was correlated positively with MPO (r=0.314, p<0.05). Moreover, a positive correlation was observed between the increased HMW ratio and MPO during treatment (r=0.304, p<0.05). HMW-APN correlates positively with MPO in patients with type 2 diabetes. Therefore, HMW-APN may exert possible pro-inflammatory effects in type 2 diabetes.
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PMID:High molecular weight adiponectin correlates positively with myeloperoxidase in patients with type 2 diabetes mellitus. 1877 66

Prostacyclin synthase (PGIS) is tyrosine nitrated in diseased animals. Whether PGIS nitration occurs in human diabetic atherosclerotic arteries has not been reported. The present study was designed to determine PGIS nitration and its association with the inflammatory response in atherosclerotic carotid arteries from patients with or without type 2 diabetes, and carotid plaques were obtained from patients who underwent carotid endarterectomy. PGIS nitration, nitric oxide synthases, adhesion molecules, myeloperoxidase, osteopontin, and matrix metalloproteinase (MMP) were measured by using immunohistochemistry and Western blotting. In low stenosis areas, diabetes enhanced reactive nitrogen species production, as evidenced by increases in 3-nitrotyrosine and PGIS nitration. In parallel, diabetes dramatically increased inflammatory markers including intracellular adhesion molecule-1, vascular adhesion molecule-1, and osteopontin. In both diabetic and nondiabetic patients, MMP-2 and MMP-9 protein levels were significantly increased in the arteries with high stenosis as compared with those with low stenosis. Moreover, diabetes enhanced inducible nitric oxide synthase expression in the plaques from low stenosis areas and up-regulated myeloperoxidase expression in the plaques from both high and low stenosis areas. These data demonstrate that diabetes preferentially increases PGIS nitration that is associated with excessive vascular inflammation in atherosclerotic carotid arteries from patients with type 2 diabetes, suggesting a possible role of tyrosine nitration of PGIS in the development of atherosclerosis in patients with diabetes.
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PMID:Enhanced tyrosine nitration of prostacyclin synthase is associated with increased inflammation in atherosclerotic carotid arteries from type 2 diabetic patients. 2034 34

Scavenging of the vasodilator nitric oxide by myeloperoxidase activity in the vasculature may contribute to hypertension. Because hydrogen peroxide is a cosubstrate of myeloperoxidase, hyperglycemia-induced oxidative stress may strengthen the relationship between myeloperoxidase and blood pressure. We investigated this relationship and its modification by hyperglycemia and oxidative stress in a population-based cohort of elderly subjects with normal glucose metabolism (n=267), impaired glucose metabolism (n=189), and type 2 diabetes (n=290). In an age- and sex-adjusted linear regression model, plasma myeloperoxidase was positively associated with systolic blood pressure (2.10 mm Hg per 1 SD increment of myeloperoxidase [95% CI: 0.66 to 3.54]), and this association was stronger at higher levels of fasting glucose (0.61 [-1.70 to 2.93], 1.33 [-1.43 to 4.10], and 3.42 [1.01 to 5.82] for increasing tertiles of glucose) and higher plasma levels of oxidized low-density lipoprotein (0.92 [-1.31 to 3.14], 2.00 [-0.71 to 4.70], and 3.58 [0.98 to 6.19] for increasing tertiles of oxidized low-density lipoprotein). Likewise, the relationship between myeloperoxidase and blood pressure was strongest under conditions associated with oxidative stress, like obesity, low high-density lipoprotein cholesterol, metabolic syndrome, and type 2 diabetes. The strength of these associations was only marginally attenuated by adjustment for other cardiovascular risk factors. Our data demonstrate that myeloperoxidase is positively and independently associated with blood pressure, and this association is strongest in subjects with (hyperglycemia-induced) oxidative stress. These observations, together with emerging evidence that myeloperoxidase-derived oxidants contribute to the initiation and propagation of cardiovascular disease, identify myeloperoxidase as a promising target for drug development.
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PMID:Hyperglycemia and oxidative stress strengthen the association between myeloperoxidase and blood pressure. 2038 72

Nonalcoholic fatty liver disease (NAFLD) is currently the most common liver disease in the world. It encompasses a histological spectrum, ranging from simple, nonprogressive steatosis to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis and hepatocellular carcinoma. While liver-related complications are confined to NASH, emerging evidence suggests both simple steatosis and NASH predispose to type 2 diabetes and cardiovascular disease. The pathogenesis of NAFLD is currently unknown, but accumulating data suggest that oxidative stress and altered redox balance play a crucial role in the pathogenesis of steatosis, steatohepatitis, and fibrosis. We will examine intracellular mechanisms, including mitochondrial dysfunction and impaired oxidative free fatty acid metabolism, leading to reactive oxygen species generation; additionally, the potential pathogenetic role of extracellular sources of reactive oxygen species in NAFLD, including increased myeloperoxidase activity and oxidized low density lipoprotein accumulation, will be reviewed. We will discuss how these mechanisms converge to determine the whole pathophysiological spectrum of NAFLD, including hepatocyte triglyceride accumulation, hepatocyte apoptosis, hepatic inflammation, hepatic stellate cell activation, and fibrogenesis. Finally, available animal and human data on treatment opportunities with older and newer antioxidant will be presented.
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PMID:Redox balance in the pathogenesis of nonalcoholic fatty liver disease: mechanisms and therapeutic opportunities. 2096 75


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