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

Common uncoupling protein 2 (UCP2) promoter polymorphism -866G/A is reported to be associated with its expression in adipose tissue and the risk of obesity in Caucasians. On the other hand, several studies suggested that UCP2 expression in beta-cells is an important determinant of insulin secretion. In the Japanese population, morbid obesity is very rare, and insulin secretion capacity is relatively low as compared with Caucasians. Because UCP2 would link to insulin secretion and obesity, it might explain this ethnic difference. Here, we report that the UCP2 promoter with the A allele showed higher promoter activity in the INS-1 beta-cell line. The frequency of the A allele is higher in our Japanese study than that in Caucasians. Type 2 diabetic patients with the A allele need insulin therapy earlier and showed higher frequency of insulin treatment. Moreover glucose-induced early insulin secretion is significantly lower in patients with the A allele. However, there was no difference in allele frequency between obese and lean type 2 diabetic patients. In conclusion, UCP2 promoter polymorphism -866G/A does not affect obesity in Japanese type 2 diabetic patients but affects its transcription in beta-cells and modulates glucose-induced insulin secretion and eventually insulin requirement in Japanese type 2 diabetic patients. Higher A allele frequency in the Japanese population might partly explain the ethnic difference of insulin secretion capacity.
Diabetes 2004 Feb
PMID:Uncoupling protein 2 promoter polymorphism -866G/A affects its expression in beta-cells and modulates clinical profiles of Japanese type 2 diabetic patients. 1474 1

On its own, glucose is a major factor for proliferation of pancreatic beta-cells and is also an essential prerequisite for IGF-I and growth hormone-induced growth of these cells. p8 was originally identified as an emergency gene product upregulated in pancreatic acinar cells in response to acute pancreatitis. p8 was further shown to be involved in a broad range of biological functions, including cell growth, growth arrest, apoptosis, and tumor development. These in part opposite actions may be related to distinct stimuli and pathways in certain conditions and cell types. Here we demonstrate that p8 is widely expressed in human pancreatic islets in vivo and in several beta-cell lines in vitro. Based on this observation, we tested the hypothesis that p8 production in pancreatic beta-cells is regulated by glucose. Incubation of rat INS-1 beta-cells with 25 mmol/l glucose resulted in a continuous increase of proliferating cell numbers. This was accompanied by a strong upregulation of p8 mRNA and protein expression, indicating that p8 is a physiological mediator of glucose-induced pancreatic beta-cell growth. Binding of glucose-activated protein kinase C (PKC) to two PKC sites within a highly conserved region of the p8 protein may be a possible mechanism linking glucose and p8 pathways leading to proliferation.
Diabetes 2004 Feb
PMID:Nuclear protein p8 is associated with glucose-induced pancreatic beta-cell growth. 1474 70

Specific activation of Ca(2+)-dependent functions is achieved by the particular dynamics and local restriction of Ca(2+) signals. It has been shown that changes in amplitude, duration, or frequency of Ca(2+) signals modulate gene transcription. Thus, Ca(2+) variations should be finely controlled within the nucleus. Although a variety of mechanisms in the nuclear membrane have been demonstrated to regulate nuclear Ca(2+), the existence of an autonomous Ca(2+) homeostasis within the nucleus is still questioned. In the pancreatic beta-cell, besides their effect on insulin secretion, Ca(2+) messages generated by nutrients also exert their action on gene expression. However, the dynamics of these Ca(2+) signals in relation to nuclear function have been explored little in islet cells. In the current study, Ca(2+) changes both in the nucleoplasm and in the cytosol of INS-1 and pancreatic beta-cells were monitored using spot confocal microscopy. We show that nutrients trigger Ca(2+) signals of higher amplitude in the nucleus than in the cytosol. These amplitude-modulated Ca(2+) signals transmitted to the nucleus might play an important role in the control of gene expression in the pancreatic beta-cell.
Diabetes 2004 Feb
PMID:Nutrients induce different Ca(2+) signals in cytosol and nucleus in pancreatic beta-cells. 1474 72

Evidence that group VIA cytosolic calcium-independent phospholipase A(2) (iPLA(2)beta) participates in beta-cell signal transduction includes the observations that inhibition of iPLA(2)beta with the bromoenol lactone suicide substrate suppresses glucose-stimulated insulin secretion and that overexpression of iPLA(2)beta amplifies insulin secretory responses in INS-1 insulinoma cells. Immunofluorescence analyses also reveal that iPLA(2)beta accumulates in the perinuclear region of INS-1 cells stimulated with glucose and forskolin. To characterize this phenomenon further, iPLA(2)beta was expressed as a fusion protein with enhanced green fluorescent protein (EGFP) in INS-1 cells so that movements of iPLA(2)beta are reflected by changes in the subcellular distribution of green fluorescence. Stimulation of INS-1 cells overexpressing iPLA(2)beta-EGFP induced greater insulin secretion and punctate accumulation of iPLA(2)beta-EGFP fluorescence in the perinuclear region. To determine the identity of organelles with which iPLA(2)beta might associate, colocalization of green fluorescence with fluorophores associated with specific trackers targeted to different subcellular organelles was examined. Such analyses reveal association of iPLA(2)beta-EGFP fluorescence with the ER and Golgi compartments. Arachidonate-containing plasmenylethanolamine phospholipid species are abundant in beta-cell endoplasmic reticulum (ER) and are excellent substrates for iPLA(2)beta. Arachidonic acid produced by iPLA(2)beta-catalyzed hydrolysis of their substrates induces release of Ca(2+) from ER stores-an event thought to participate in glucose-stimulated insulin secretion.
Diabetes 2004 Feb
PMID:Beta-cell calcium-independent group VIA phospholipase A(2) (iPLA(2)beta): tracking iPLA(2)beta movements in response to stimulation with insulin secretagogues in INS-1 cells. 1474 86

The beta-cell loss seen in diabetes mellitus could be monitored clinically by positron emission tomography (PET) if imaging agents were sufficiently specific for beta-cells to overcome the high ratio of non-beta-cell to beta-cell tissue in pancreas. In this report, we present a screening assay for identifying beta-cell-specific compounds that is based on the relative accumulation and retention by islet, INS-1, and exocrine (PANC-1) cells of candidate molecules. Molecules thought to have a high affinity for beta-cells were tested and included glibenclamide, tolbutamide, serotonin, L-DOPA, dopamine, nicotinamide, fluorodeoxyglucose, and fluorodithizone. Glibenclamide and fluorodithizone were the most specific, but the specificity ratios fell well below those needed to attain robust signal to background ratio as a PET imaging agent for quantifying beta-cell mass. In vivo tests of the biodistribution of glibenclamide and fluorodithizone in rats indicated that the compounds were not specifically associated with pancreas, bearing out the predictions of the in vitro screen.
 ...
PMID:Systematic screening of potential beta-cell imaging agents. 1475 Dec 28

A number of factors have been reported to affect insulin synthesis in beta-cells. Although glucose is the most important regulator of insulin gene expression in pancreatic beta-cells, the mechanisms whereby glucose stimulates insulin gene transcription in response to changes in glucose concentration have not been clarified yet. In this study, we examined the role of the Ca(2+)/calmodulin (CaM)-dependent protein kinase (CaM-K) cascade in transcriptional activation of insulin. RT-PCR, Western blotting, and immunohistochemical staining analysis revealed that CaM-K kinase-alpha (CaM-KKalpha) and CaM-KIV were localized in rat pancreatic beta-cells and their cell line, INS-1. Exposure of INS-1 cells to 11.2 mmol/l glucose elicited an increase of insulin promoter activity as well as upregulation of CaM-KIV activity within 2 min after stimulation. We investigated the influence on insulin promoter activity of the constitutively active form (CaM-KIVc) or dominant-negative mutant (CaM-KIVdn) of CaM-KIV in transfected INS-1 cells. CaM-KIVc alone was sufficient, and the upstream kinase, CaM-KK, was enhanced to upregulate the insulin promoter activity in INS-1 cells. Furthermore, cotransfection of CaM-KIVdn suppressed to a significant degree the glucose-upregulated activity of the insulin promoter. Taken together, these results indicated that the CaM-KK/CaM-KIV cascade might play an important role in glucose-upregulated transcriptional activation of the insulin gene.
Diabetes 2004 Jun
PMID:The role of calcium/calmodulin-dependent protein kinase cascade in glucose upregulation of insulin gene expression. 1516 51

Epidemiological studies have identified nitrosamines as a risk factor for Type I (insulin dependent) diabetes mellitus. These compounds require bioactivation by cytochrome P450 2E1 (CYP2E1) for exertion of their toxic effects. Two mammalian insulin secreting pancreatic beta-cell lines BRIN BD11h2E1 and INS-1h2E1, which express human full length CYP2E1 cDNA, were used to elucidate the role of CYP2E1-mediated nitrosamine bioactivation in pancreatic beta-cell dysfunction and destruction. These cell lines were shown to metabolise dimethylnitrosamine to produce formaldehyde at rates of 3.41 +/- 0.24 and 3.65 +/- 0.26 nmol/minmg microsomal protein, respectively. Following incubation with various concentrations of the nitrosamines dimethylnitrosamine, N-nitrosopyrrolidine and 1-nitrospiperidine, all of which are bioactivated by CYP2E1, cytotoxicity and DNA damage were assessed using either the neutral red assay or comet assay respectively. Exposure of CYP2E1 expressing cells to nitrosamines resulted in significant dose-dependent decreases in cell viability, which were not seen in cells which did not express CYP2E1. Following culture with nitrosamine concentrations as low as 2.5mM 1-nitrosopiperidine, cell viability was significantly lower in BRIN BD11h2E1 and INS-1h2E1 cell lines in comparison to the BRIN BD11 and INS-1 parental cell lines (72.5 +/- 4.96 and 66.4 +/- 3.09% in BRIN BD11h2E1 and INS-1h2E1 versus 109.0 +/- 3.40 and 100.0 +/- 3.25% in BRIN BD11 and INS-1 respectively, P < 0.001). The highest dose of any of the nitrosamines tested failed to significantly reduce cell viability in the cells which lacked CYP2E1. Expression of CYP2E1 did not cause any change in the basal level of DNA damage in any of the cell lines. However, 16 h exposure to various nitrosamines resulted in significant dose-dependent DNA damage in the BRIN BD11h2E1 and INS-1h2E1 cells compared to their respective non CYP2E1-expressing parental controls, e.g. DNA damage increased from 34.38 +/- 1.25 to 44.01 +/- 1.56% DNA in comet tail in BRIN BD11h2E1 cells incubated with 10 or 40 mM N-nitrosopyrrolidine, respectively (P < 0.001). Similar treatment of the BRIN BD11 and INS-1 cell lines did not result in a significant increase in DNA damage (20.33 +/- 1.0 and 22.4 +/- 0.98% DNA in comet tail). The pancreatic beta-cell is richly vascularised and expresses CYP2E1. This study suggests that expression of human CYP2E1 in pancreatic beta-cells make them highly susceptible to cytotoxicity and DNA damage by nitrosamines and other agents bioactivated by CYP2E1.
 ...
PMID:DNA damage and cytotoxicity in pancreatic beta-cells expressing human CYP2E1. 1524 18

Silencing gene expression by RNA interference (RNAi) can provide insight into gene function but requires efficient delivery of small interfering RNAs (siRNAs) into cells. Introduction of exogenous nucleic acids can be especially difficult in cultured pancreatic islets. This article describes a method for making recombinant adenoviruses that efficiently drive expression of siRNAs in islet beta-cells and a beta-cell-derived cell line. Transduction with a virus expressing an siRNA specific for GLUT2 reduced GLUT2 mRNA and protein levels by 80% in the INS-1-derived beta-cell line, 832/13, and GLUT2 protein levels by >90% in primary rat islets. Another virus expressing an siRNA specific for glucokinase (GK) caused 80% suppression of GK mRNA and 50% suppression of GK protein levels in 832/13 cells. These experiments validate recombinant adenoviral RNAi vectors as a useful tool for suppression of the expression of specific genes in pancreatic islets and beta-cell lines. Advantages of this approach include 1) the high efficiency of adenovirus-mediated gene transfer in insulinoma cell lines and rat islets and 2) the rapidity with which RNAi constructs can be prepared and tested relative to stable-transfection strategies.
Diabetes 2004 Sep
PMID:An adenovirus vector for efficient RNA interference-mediated suppression of target genes in insulinoma cells and pancreatic islets of langerhans. 1533 26

SLC30A8, a novel member of the zinc transporter (ZnT) family, was identified by searching the human genomic and expressed sequence tag (EST) databases with the amino acid sequence of all known human ZnT. The protein (369 amino acids) predicted from this gene, ZnT-8, contains six transmembrane domains and a histidine-rich loop between transmembrane domains IV and V, like the other ZnT proteins. We demonstrated by RT-PCR on cDNA libraries and human tissue extracts that the ZnT-8 gene is solely transcribed in the pancreas, mainly in the islets of Langerhans. The gene, named SLC30A8, was cloned and sequenced. Confocal immunofluorescence analysis revealed that a ZnT-8-EGFP (enhanced green fluorescent protein) fusion product colocalized with insulin in the secretory pathway granules of the insulin-secreting INS-1 cells. Exposure of the ZnT-8-EGFP stably expressing HeLa cells to 75 micromol/l zinc caused an accumulation of zinc in intracellular vesicles compared with cells expressing EGFP alone. These results identified ZnT-8 as a ZnT specific to the pancreas and expressed in beta-cells. Because ZnT-8 facilitates the accumulation of zinc from the cytoplasm into intracellular vesicles, ZnT-8 may be a major component for providing zinc to insulin maturation and/or storage processes in insulin-secreting pancreatic beta-cells.
Diabetes 2004 Sep
PMID:Identification and cloning of a beta-cell-specific zinc transporter, ZnT-8, localized into insulin secretory granules. 1533 42

Ascorbic acid is necessary for optimal insulin secretion from pancreatic islets. We evaluated ascorbate recycling and whether it is impaired by increased glucose metabolism in the rat beta-cell line INS-1. INS-1 cells, engineered with the potential for overexpression of glucokinase under the control of a tetracycline-inducible gene expression system, took up and reduced dehydroascorbic acid to ascorbate in a concentration-dependent manner that was optimal in the presence of physiologic D-glucose concentrations. Ascorbate uptake did not affect intracellular GSH concentrations. Whereas depletion of GSH in culture to levels about 25% of normal also did not affect the ability of the cells to reduce dehydroascorbic acid, more severe acute GSH depletion to less than 10% of normal levels did impair dehydroascorbic acid reduction. Culture of inducible cells in 11.8 mM D-glucose and doxycycline for 48 h enhanced glucokinase activity, increased glucose utilization, abolished D-glucose-dependent insulin secretion, and increased generation of reactive oxygen species. The latter may have contributed to subsequent decreases in the ability of the cells both to maintain intracellular ascorbate and to recycle it from dehydroascorbic acid. Cultured beta cells have a high capacity to recycle ascorbate, but this is sensitive to oxidant stress generated by increased glucose metabolism due to culture in high glucose concentrations and increased glucokinase expression. Impaired ascorbate recycling as a result of increased glucose metabolism may have implications for the role of ascorbate in insulin secretion in diabetes mellitus and may partially explain glucose toxicity in beta cells.
 ...
PMID:Ascorbic acid recycling by cultured beta cells: effects of increased glucose metabolism. 1547 12


<< Previous 1 2 3 4 5 6 7 8 9 10