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)

Complications of diabetes have a genetic influence. Since increased inducible nitric oxide synthase (iNOS) gene ( NOS2A) expression can contribute to tissue damage, NOS2A is a worthy candidate for such a role. We therefore tested a 4-bp insertion/deletion (+/-) polymorphism 0.7 kb upstream of NOS2A for association with complications in type 2 diabetes patients, and also performed transient transfection experiments to examine the effect of this variant on promoter activity in kidney cells in culture. We investigated 379 Caucasian type 2 diabetes patients of British/European descent, 93 of whom had microalbuminuria, 26 overt nephropathy, 46 retinopathy, and 73 clinical neuropathy. Genotyping for the variant was carried out by PCR and automated Genescan analysis. Transient transfection studies involved the renal HEK 293 cell line and luciferase reporter gene constructs containing 1.1 kb of 5'-flanking DNA from '+' or '-' allele homozygotes. We found that the '+' allele frequency in patients without microalbuminuria was 12%, but was 23% in those with microalbuminuria ( P=0.0005), and was 26% in those with nephropathy ( P=0.0007), 22% in those with retinopathy ( P=0.037), and 23% in those with neuropathy ( P=0.045). The odds ratios for homozygote +/+ to have microalbuminuria or nephropathy were 2.4 (95% CI 1.4-4.2, P=0.0023) and 5.4 (95% CI 1.8-16, P=0.0009), respectively. Luciferase reporter gene constructs containing 1 kb of NOS2A promoter DNA for each allele were made and sequence analysis confirmed that the +/- variation was the only sequence difference present. Transient transfection of these into HEK 293 cells revealed 25 times higher reporter gene activity for the '+' allele compared with the '-' allele. Gel shift analysis with 30mer oligonucleotides corresponding to each allele showed specific binding to nuclear extracts, being greater for the '+' allele. Thus the '+' allele of the NOS2A promoter variant may confer higher iNOS expression, and could contribute to complications of type 2 diabetes, especially in the approximately 5% of patients homozygous for this variant.
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PMID:Association of a functional inducible nitric oxide synthase promoter variant with complications in type 2 diabetes. 1190 46

Mutations in the hepatocyte nuclear factor (HNF)-1alpha gene have been linked to subtype 3 of maturity-onset diabetes of the young (MODY), a disease characterized by a primary defect in insulin secretion. Here we show that the human GLUT2 gene is closely regulated by HNF-1alpha via sequences downstream of the transcriptional start site by interaction with transcriptional co-activator p300. The promoter region of the human GLUT2 gene was subcloned into luciferase expression plasmids that were transfected together with HNF-1alpha expression plasmid into a pancreatic beta-cell line, HIT-T15, to evaluate transcriptional activities. HNF-1alpha enhanced human GLUT2 promoter activity sixfold. Site-direct mutagenesis and footprint analyses showed that the HNF-1alpha binding site (+200 to +218) is critical in human GLUT2 gene expression. Furthermore, mammalian two-hybrid and immunoprecipitation studies revealed the transactivation domain of HNF-1alpha (amino acids 391-540) to interact with both the NH(2)-terminal region (amino acids 180-662) and the COOH-terminal region (amino acids 1,818-2,079) of p300. These findings demonstrated that HNF-1alpha binds to the 5'-untranslated region of GLUT2 and that p300 acts as a transcriptional co-activator for HNF-1alpha. In addition, these results provided new insight into the regulatory function of HNF-1alpha by suggesting a molecular basis for human GLUT2 gene expression.
Diabetes 2002 May
PMID:Hepatocyte nuclear factor-1alpha recruits the transcriptional co-activator p300 on the GLUT2 gene promoter. 1197 37

Experiments in vascular smooth muscle cells (SMCs) indicate that the transcription factor cAMP response element-binding protein (CREB), the cyclic nucleotide response element-binding protein, suppresses expression of the platelet-derived growth factor-alpha receptor gene (PDGFRalpha). Adenovirus-mediated expression of constitutively active CREB mutants decreases PDGFRalpha mRNA, PDGFRalpha protein, and PDGFRalpha promoter-luciferase reporter activity in cultured SMCs. Expression of dominant negative CREB protein, A-CREB, increases PDGFRalpha protein content and the PDGFRalpha-promoter activity in SMCs. Active CREB prevents activation of PDGFRalpha promoter-luciferase reporter activity by CCAAT/enhancer-binding protein-delta (C/EBPdelta), shown to mediate IL-1beta stimulation of PDGFRalpha expression. Exposure of cultured SMCs to high glucose or reactive oxidant stress, which decrease CREB protein content and activity, increases PDGFRalpha protein content and promoter activity. Expression of active CREB blunts reactive oxidant stress-induced PDGFRalpha accumulation in SMCs. Loss of CREB protein in aortic walls of rats with streptozotocin-induced diabetes is accompanied by an increase in PDGFRalpha content. In Ob/Ob mice (which demonstrate reduced aortic wall CREB content vs. Ob/- controls), treatment with the peroxisomal proliferator-activated receptor gamma rosiglitazone increases CREB content and decreases PDGFRalpha content in the aortic wall. Thus, both in vitro and in vivo loss of CREB content and activity and subsequent accumulation of PDGFRalpha may contribute to SMC activation during diabetes.
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PMID:Content and activity of cAMP response element-binding protein regulate platelet-derived growth factor receptor-alpha content in vascular smooth muscles. 1213 May 57

Advanced glycation end products (AGEs) play an important role in the development of angiopathy in diabetes mellitus and atherosclerosis. Here, we show that adducts of N(epsilon)-(carboxymethyl)lysine (CML), a major AGE, and bovine serum albumin (CML-BSA) stimulated gamma-glutamylcysteine synthetase (gamma-GCS), which is a key enzyme of glutathione (GSH) synthesis, in RAW264.7 mouse macrophage-like cells. CML-BSA stimulated the expression of gamma-GCS heavy subunit (h) time- and dose-dependently and concomitantly increased GSH levels. CML-BSA also stimulated DNA-binding activity of activator protein-1 (AP-1) within 3h, but the stimulatory effect decreased in 5h, and nuclear factor-kappaB (NF-kappaB) with a peak activity at 1h and the stimulatory effect diminished in 3h. Studies of luciferase activity of the gamma-GCSh promoter showed that deletion and mutagenesis of the AP-1-site abolished CML-BSA-induced up-regulation, while that of NF-kappaB-site did not affect CML-BSA-induced activity. CML-BSA also stimulated the activity of protein kinase C, Ras/Raf-1, and MEK/ERK1/2. Inhibition of ERK1/2 abolished CML-BSA-stimulated AP-1 DNA-binding activity and gamma-GCSh mRNA expression. Our results suggest that induction of gamma-GCS by CML adducts seems to increase the defense potential of cells against oxidative stress produced during glycation processes.
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PMID:Nepsilon-(Carboxymethyl)lysine induces gamma-glutamylcysteine synthetase in RAW264.7 cells. 1214 23

Glucose responsiveness is a fundamental metabolic feature of pancreatic beta-cells. Glucose-regulated transcription of the insulin gene is in part mediated via the homeobox transcription factor PDX-1. Another islet protein and diabetes autoantigen, glutamic acid decarboxylase (GAD), has been shown to be subject to regulation by glycemia. We have studied the mRNA level of two isoforms of GAD, GAD(65) and GAD(67), and found that GAD(67) but not GAD(65) mRNA steady-state level is regulated by glucose. By transfection of a rat GAD(67) promoter-driven luciferase reporter gene into primary rat islet cells, we demonstrate glucose-regulated expression of the reporter gene. We show that PDX-1 is able to bind to two TAAT-boxes in the GAD(67) promoter and that functional disruption of these two PDX-1 binding elements has an additive effect in severely impairing glucose responsiveness of the GAD(67) promoter. These data strongly suggest that PDX-1 is involved in glucose-regulated expression of GAD(67).
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PMID:PDX-1 mediates glucose responsiveness of GAD(67), but not GAD(65), gene transcription in islets of Langerhans. 1215 Sep 38

Homocysteine metabolism is altered in diabetic patients. Cystathionine beta-synthase (CBS), a key enzyme involved in the transsulfuration pathway, which irreversibly converts homocysteine to cysteine, catalyzes the condensation of serine and homocysteine to cystathionine. Studies in streptozotocin-induced diabetic rats have shown that CBS enzyme activity is elevated in the liver but not in the kidney, and this effect is reversed by insulin treatment. To determine whether these effects resulted from alterations at the level of gene transcription, CBS mRNA was measured in diabetic and insulin-treated diabetic rats. CBS mRNA levels were found to be markedly higher in streptozotocin-induced diabetic rat livers; these were reduced by insulin administration. In H4IIE cells, a rat hepatoma cell culture model, glucocorticoids increased the cellular levels of CBS enzyme protein and CBS mRNA; insulin inhibited this stimulatory effect. Treatment with insulin also decreased CBS levels in HepG2 cells, a human hepatoma cell line. Nuclear run-on experiments in the rat cells confirmed that stimulation of CBS gene expression by glucocorticoids and the inhibition by insulin occurred at the transcriptional level. Transient transfections of HepG2 cells with a CBS-1b promoter luciferase reporter construct showed that the promoter activity was decreased by 70% after insulin treatment. These results show that insulin has a direct role in regulating homocysteine metabolism. Altered insulin levels in diseases such as diabetes may influence homocysteine metabolism by regulating the hepatic transsulfuration pathway.
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PMID:Hormonal regulation of cystathionine beta-synthase expression in liver. 1219 28

The expression of the matrix cytokine osteopontin (OPN) is up-regulated in aortic vascular smooth muscle cells (VSMCs) by diabetes. OPN expression in cultured VSMCs is reciprocally regulated by glucose and 2-deoxyglucose (2-DG; inhibitor of cellular glucose metabolism). Systematic analyses of OPN promoter-luciferase reporter constructs identify a CCTCATGAC motif at nucleotides -80 to -72 relative to the initiation site that supports OPN transcription in VSMCs. The region -83 to -45 encompassing this motif confers basal and glucose- and 2-DG-dependent transcription on an unresponsive promoter. Competition and gel mobility supershift assays identify upstream stimulatory factor (USF; USF1:USF2) and activator protein-1 (AP1; c-Fos:c-Jun) in complexes binding the composite CCTCATGAC element. Glucose up-regulates both AP1 and USF binding activities 2-fold in A7r5 cells and selectively up-regulates USF1 protein levels. By contrast, USF (but not AP1) binding activity is suppressed by 2-DG and restored by glucose treatment. Expression of either USF or AP1 activates the proximal OPN promoter in A7r5 VSMCs in part via the CCTCATGAC element. Moreover, glucose stimulates the transactivation functions of c-Fos and USF1, but not c-Jun, in one-hybrid assays. Mannitol does not regulate binding, transactivation functions, USF1 protein accumulation, or OPN transcription. Thus, OPN gene transcription is regulated by USF and AP1 in aortic VSMCs, entrained to changes in cellular glucose metabolism.
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PMID:Osteopontin transcription in aortic vascular smooth muscle cells is controlled by glucose-regulated upstream stimulatory factor and activator protein-1 activities. 1220 Apr 34

Proximal tubular renal epithelial cells may contribute to the pathogenesis of renal interstitial fibrosis in diabetes by generation of cytokines such as transforming growth factor (TGF)-beta1. We have previously demonstrated that proximal tubular renal epithelial cell TGF-beta1 synthesis may be modulated by elevated glucose concentration and by cytokines such as platelet-derived growth factor (PDGF). The aim of the current study was to characterize the mechanism by which glucose and PDGF synergistically stimulate the generation of TGF-beta1. Addition of either 25 mmol/L of D-glucose or low-dose PDGF increased TGF-beta1 mRNA expression without stimulation of TGF-beta1 protein synthesis. In contrast sequential stimulation with 25 mmol/L of D-glucose for 48 hours followed by low-dose (25 ng/ml) PDGF led to a significant increase in TGF-beta1 synthesis. Elevated glucose concentration stimulated de novo gene transcription as assessed by stimulation of a TGF-beta1 promoter-luciferase construct. This led to induction of a poorly translated TGF-beta1 transcript determined by polysome analysis. PDGF at low dose did not influence TGF-beta1 transcription, but led to alteration in TGF-beta1 mRNA stability and translation. Without a previous glucose-induced increase in the amount of TGF-beta1 transcript, PDGF did not stimulate significant TGF-beta1 protein synthesis. At a high dose (100 ng/ml) PDGF stimulated TGF-beta1 synthesis independent of glucose concentration. This was associated with increased TGF-beta1 gene transcription and alteration in TGF-beta1 mRNA translational efficiency. In conclusion the data suggests that in diabetic nephropathy, the role of glucose is to lower the threshold at which a stimulus such as PDGF stimulates TGF-beta1 protein synthesis. The data also suggest that independent regulation of TGF-beta1 transcription and translation by glucose and PDGF account for their synergistic effect on TGF-beta1 protein synthesis. We hypothesize that the role of glucose in diabetic nephropathy is to prime the kidney for an injurious response to other stimuli.
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PMID:Independent regulation of transforming growth factor-beta1 transcription and translation by glucose and platelet-derived growth factor. 1221 33

Low HDL cholesterol is a frequent cardiovascular risk factor in diabetes. Because of its pivotal role for the regulation of HDL plasma levels, we investigated in vivo and in vitro regulation of the ATP-binding cassette transporter A1 (ABCA1) by insulin and metabolites accumulating in diabetes. Compared with euglycemic control mice, ABCA1 gene expression was severely decreased in the liver and peritoneal macrophages of diabetic mice. Treatment with insulin restored this deficit. Incubation of cultivated HepG2 hepatocytes and RAW264.7 macrophages with unsaturated fatty acids or acetoacetate, but not with insulin, glucose, saturated fatty acids, or hydroxybutyrate, downregulated ABCA1 mRNA and protein. The suppressive effect of unsaturated fatty acids and acetoacetate became most obvious in cells stimulated with oxysterols or retinoic acid but was independent of the expression of the thereby regulated transcription factors liver-X-receptor alpha (LXRalpha) and retinoid-X-receptor alpha (RXRalpha), respectively. Unsaturated fatty acids and acetoacetate also reduced ABCA1 promotor activity in RAW264.7 macrophages that were transfected with a 968-bp ABCA1 promotor/luciferase gene construct. As the functional consequence, unsaturated fatty acids and acetoacetate inhibited cholesterol efflux from macrophages. Downregulation of ABCA1 by unsaturated fatty acids and acetoacetate may contribute to low HDL cholesterol and increased cardiovascular risk of diabetic patients.
Diabetes 2002 Oct
PMID:Polyunsaturated fatty acids and acetoacetate downregulate the expression of the ATP-binding cassette transporter A1. 1235 28

The insulin gene is specifically expressed in beta-cells of the Langerhans islets of the pancreas, and its transcription is regulated by the circulating glucose level. Previous reports have shown that an unidentified beta-cell-specific nuclear factor binds to a conserved cis-regulatory element called RIPE3b and is critical for its glucose-regulated expression. Based on the sequence similarity of the RIPE3b element and the consensus binding sequence of the Maf family of basic leucine zipper transcription factors, we here identified mammalian homologue of avian MafA/L-Maf, an eye-specific member of the Maf family, as the RIPE3b-binding transcriptional activator. Reverse transcription-PCR analysis showed that mafA mRNA is detected only in the eyes and in pancreatic beta-cells and not in alpha-cells. MafA protein as well as its mRNA is up-regulated by glucose, consistent with the glucose-regulated binding of MafA to the RIPE3b element in beta-cell nuclear extracts. In transient luciferase assays, we also showed that expression of MafA greatly enhanced insulin promoter activity and that a dominant-negative form of MafA inhibited it. Therefore, MafA is a beta-cell-specific and glucose-regulated transcriptional activator for insulin gene expression and thus may be involved in the function and development of beta-cells as well as in the pathogenesis of diabetes.
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PMID:MafA is a glucose-regulated and pancreatic beta-cell-specific transcriptional activator for the insulin gene. 1236 92


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