Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucagon-like peptide-1 (GLP-1) is an incretin hormone derived from the proglucagon gene, capable of regulating the transcription of the three major genes that determine the pancreatic beta-cell-specific phenotype: insulin, GLUT-2, and glucokinase. The aim of this study was to investigate the potential role of GLP-1 for the gene therapy of glucose-insensitive pancreatic beta-cells. We transfected mouse insulinoma cells with a DNA fragment of the human proglucagon gene containing the nucleotide sequence encoding for human GLP-1 but lacking the coding region for glucagon. Two constructs were generated: In one, the expression of GLP-1 was under the control of the cytomegalovirus (CMV) promoter (CMV/GLP-1), and the second was regulated by the rat insulin II promoter (RIP)/GLP-1). Northern blot, HPLC, and RIA analyses confirmed that the minigene was transcribed and the protein appropriately translated, processed, and secreted in the extracellular environment. Gene expression studies revealed that although CMV/GLP-1 cells did not gain a greater glucose sensitivity as a result of the transfection with GLP-1, compared with cells transfected with the plasmid alone, RIP/GLP-1 was capable of regulating the gene expression of insulin and GLP-1 based on the concentration of glucose in the culture medium. Detection of the counterpart proteins (insulin and GLP-1) in the culture medium paralleled the observation derived from the Northern blot analysis. GLP-1 action was mediated by an IDX-1 (islet/duodenum homeobox-1) dependent transactivation of the endogenous insulin promoter, as demonstrated by gel shift analysis. This was further suggested by a significant increase of the glucose-dependent binding of IDX-1 to the insulin promoter in RIP/GLP-1 cells but not in CMV/GLP-1 cells or control cells. Finally, we observed that although the GLP-1-dependent secretion of insulin was mediated by an increase in cAMP levels, the transcription of the insulin gene, in response to GLP-1, was in large part cAMP independent. The present study lays the research foundation to investigate the potential use of GLP-1 for the gene or cell therapy of diabetes.
 ...
PMID:Transfection of pancreatic-derived beta-cells with a minigene encoding for human glucagon-like peptide-1 regulates glucose-dependent insulin synthesis and secretion. 1219 67

Ca(2+)/calmodulin-dependent protein kinase II is a member of a broad family of ubiquitously expressed Ca(2+) sensing serine/threonine-kinases. Ca(2+)/calmodulin-dependent protein kinase II is highly expressed in insulin secreting cells and is associated with insulin secretory granules and has been proposed to play an important role in exocytosis or in insulin granule transport to release sites. To elucidate its function the antisense sequence of the major beta-cell subtype, Ca(2+)/calmodulin-dependent protein kinase II delta(2), was stably expressed in INS-1 rat insulinoma cells. This caused a loss of Ca(2+)/calmodulin-dependent protein kinase II delta(2) expression at the mRNA and protein level, while the expression of the 95% homologous Ca(2+)/calmodulin-dependent protein kinase II gamma and of beta-cell specific proteins such as the homeodomain factor pancreatic-duodenal homeobox factor-1 (PDX-1, also referred to as islet/duodenum homeobox-1, IDX-1, insulin promoter factor-1, IPF-1 and somatostatin transactivating factor-1, STF-1), the glucagon-like peptide-1 (GLP-1) receptor and K(ATP)-channels K(IR)6.2/SUR-1 (sulfonylurea receptor-1) was not altered. Unexpectedly, the cells showed a large reduction of insulin gene expression, which was due to reduced insulin gene transcription. Electrophoretic mobility shift assays of PDX-1 binding to the insulin promoter A1 and E2/A3A4 elements showed additional bands indicating alterations of PDX-1 complex formation. Stable over expression of Ca(2+)/calmodulin-dependent protein kinase II delta(2), by contrast, was associated with elevated expression of insulin mRNA. Therefore, we conclude that Ca(2+)/calmodulin-dependent protein kinase II delta(2) links fuel-dependent increases in intracellular Ca(2+) concentrations to transcriptional regulation of genes related to the metabolic control of insulin secretion.
 ...
PMID:Ca2+/calmodulin-dependent protein kinase II delta2 regulates gene expression of insulin in INS-1 rat insulinoma cells. 1260 Aug 4

To explore induced islet neogenesis in the liver as a strategy for the treatment of diabetes, we used helper-dependent adenovirus (HDAD) to deliver the pancreatic duodenal homeobox-1 gene (Ipf1; also known as Pdx-1) to streptozotocin (STZ)-treated diabetic mice. HDAD is relatively nontoxic as it is devoid of genes encoding viral protein. Mice treated with HDAD-Ipf1 developed fulminant hepatitis, however, because of the exocrine-differentiating activity of Ipf1. The diabetes of STZ mice was partially reversed by HDAD-mediated transfer of NeuroD (Neurod), a factor downstream of Ipf1, and completely reversed by a combination of Neurod and betacellulin (Btc), without producing hepatitis. Treated mice were healthy and normoglycemic for the duration of the experiment (>120 d). We detected in the liver insulin and other islet-specific transcripts, including proinsulin-processing enzymes, beta-cell-specific glucokinase and sulfonylurea receptor. Immunocytochemistry detected the presence of insulin, glucagon, pancreatic polypeptide and somatostatin-producing cells organized into islet clusters; immuno-electron microscopy showed typical insulin-containing granules. Our data suggest that Neurod-Btc gene therapy is a promising regimen to induce islet neogenesis for the treatment of insulin-dependent diabetes.
 ...
PMID:NeuroD-betacellulin gene therapy induces islet neogenesis in the liver and reverses diabetes in mice. 1272 55

The aim of this work was to study the possible relationship between pancreatic duodenal homeobox-1 (Pdx-1) and islet neogenesis-associated protein (INGAP) during induced islet neogenesis. Pregnant hamsters were fed with (S) and without (C) sucrose, and glycemia, insulin secretion in vitro, and pancreas immunomorphometric parameters were measured in their 7-day-old offspring. S offspring had significantly lower glycemic levels than C animals. Insulin release in response to increasing glucose concentrations in the incubation medium (2-16 mM glucose) did not increase in pancreata from either C or S offspring. However, pancreata from S offspring released more insulin than those from C animals. In S offspring, beta-cell mass, beta-cell replication rate and islet neogenesis increased significantly, with a simultaneous decrease in beta-cell apoptotic rate. INGAP- and Pdx-1-positive cell mass also increased in the islets and among acinar and duct cells. We found two subpopulations of Pdx-1 cells: INGAP-positive and INGAP-negative. Pdx-1/INGAP-positive cells did not stain with insulin, glucagon, somatostatin, pancreatic polypeptide, or neurogenin 3 antibodies. The increment of Pdx-1/INGAP-positive cells represented the major contribution to the Pdx-1 cell mass increase. Such increments varied among pancreas subsectors: ductal>insular>extrainsular. Our results suggested that INGAP participates in the regulation of islet neogenesis, and Pdx-1/INGAP-positive cells represent a new stem cell subpopulation at an early stage of development, highly activateable in neogenesis.
 ...
PMID:Pancreatic duodenal homeobox-1 and islet neogenesis-associated protein: a possible combined marker of activateable pancreatic cell precursors. 1274 13

Glucagon-like peptide-1 (GLP-1, 7-36) is capable of restoring normal glucose tolerance in aging, glucose-intolerant Wistar rats and is a potent causal factor in differentiation of human islet duodenal homeobox-1-expressing cells into insulin-releasing beta cells. Here we report stable isotope-based dynamic metabolic profiles of rat pancreatic epithelial (ARIP) and human ductal tumor (PANC-1) cells responding to 10 nM GLP-1 treatment in 48 h cultures. Macromolecule synthesis patterns and substrate flow measurements using gas chromatography/mass spectrometry (MS) and the stable [1,2-13C2]glucose isotope as the tracer showed that GLP-1 induced a significant 20% and 60% increase in de novo fatty acid palmitate synthesis in ARIP and PANC-1 cells, respectively, and it also induced a significant increase in palmitate chain elongation into stearate utilizing glucose as the primary substrate. Distribution of 13C in other metabolites indicated no changes in the rates of nucleic acid ribose synthesis, glutamate oxidation, or lactate production. Tandem high-performance liquid chromatography-ion trap MS analysis of the culture media demonstrated mass insulin secretion by GLP-1-treated tumor cells. Metabolic profile changes in response to GLP-1-induced cell differentiation include selective increases in de novo fatty acid synthesis from glucose and consequent chain elongation, allowing increased membrane formation and greater insulin availability and release.
 ...
PMID:GLP-1 stimulates glucose-derived de novo fatty acid synthesis and chain elongation during cell differentiation and insulin release. 1277 69

Embryonic stem (ES) cells differentiating in vitro reproduce many facets of early embryonic development, including the expression of developmentally regulated transcription factors and the differentiation of multipotent precursor cells. ES cells were evaluated for their ability to differentiate into pancreatic and islet lineage-restricted stages including pancreatic duodenal homeobox 1 (PDX1)-positive pancreatic precursor cells, early endocrine cell progenitors, and islet hormone-producing cells. Following growth and differentiation in nonselective medium containing serum, murine ES cells spontaneously differentiated into cells individually expressing each of the four major islet hormones: insulin, glucagon, somatostatin, and pancreatic polypeptide. PDX1 immunostaining cells appeared first, before hormone-positive cells had emerged. Hormone-positive cells appeared within focal clusters of cells coexpressing PDX1 and the nonclassical hormone markers peptide YY (YY) and islet amyloid polypeptide (IAPP) in combination with the definitive hormones, characteristic of endocrine cells appearing during early pancreaticogenesis. This system allows the investigation of many facets of islet development since it promotes the appearance of the complete range of islet phenotypes and reproduces important developmental stages of normal islet cytodifferentiation in differentiating ES cell cultures.
 ...
PMID:Pancreatic precursors and differentiated islet cell types from murine embryonic stem cells: an in vitro model to study islet differentiation. 1288 18

To identify the genes that determine differentiation phenotypes, we compared gene expression of pancreatic islet beta- and alpha-cells, which are derived from the common precursor and secrete insulin and glucagon, respectively. The expression levels of homeotic genes including Hox genes known to determine region specificity in the antero-posterior (AP) body axis, tissue-specific homeobox genes, and other 8,734 genes were compared in a beta- and alpha-cell line of MIN6 and alpha TC1.6. The expression of homeotic genes were surveyed with reverse transcription-polymerase chain reaction (RT-PCR) using degenerate primers corresponding to invariant amino acid sequences within the homeodomain and subsequently with specific primers. Expression of Hoxc6, Hoxc9, Hoxc10, Pdx1, Cdx2, Gbx2, Pax4, and Hlxb9 genes in MIN6 was higher than those in alpha TC1.6, while expression of Hoxa2, Hoxa3, Hoxa5, Hoxa6, Hoxa7, Hoxa9, Hoxa10, Hoxa13, Hoxb3, Hoxb5, Hoxb6, Hoxb13, Hoxb8, and Brain4 genes in alpha TC1.6 was higher than those in MIN6. Out of 8,734 mouse genes screened with high-density mouse cDNA microarrays for MIN6- and alpha TC1.6-derived cDNA, 58 and 25 genes were differentially over- and under-expressed in MIN6, respectively. GLUTag, which is derived from a large bowel tumor and expresses the proglucagon gene, showed a comparatively similar expression profile to that of alpha TC1.6 in both homeotic and other genes analyzed in cDNA microarray. Our results are consistent with the interpretation that not only the tissue-specific homeotic genes, but also Hox genes are related to differentiation phenotypes of pancreatic beta- and alpha-cells rather than their regional specification of the body in vertebrates.
 ...
PMID:Differentiation phenotypes of pancreatic islet beta- and alpha-cells are closely related with homeotic genes and a group of differentially expressed genes. 1509 91

Glucagon-like peptide-1 (GLP-1) regulates energy intake, gastrointestinal motility, and nutrient disposal. The relative importance of the islet beta-cell for GLP-1 actions remains unclear. We determined the role of the islet beta-cell and the pancreatic duodenal homeobox-1 (Pdx1) transcription factor for GLP-1 receptor (GLP-1R)-dependent actions through analysis of mice with beta-cell-specific inactivation of the Pdx1 gene (beta-cell(Pdx1-/-) mice). The GLP-1R agonist exendin-4 (Ex-4) reduced glycemic excursion following intraperitoneal (i.p.) glucose challenge in control littermates (beta-cell(Pdx1+/+) mice) but not in beta-cell(Pdx1-/-) mice. Similarly, Ex-4 failed to increase levels of plasma insulin, pancreatic insulin content, and pancreatic insulin mRNA transcripts in beta-cell(Pdx1-/-) mice. Furthermore, Ex-4 significantly increased beta-cell proliferation and reduced beta-cell apoptosis in beta-cell(Pdx1+/+) mice but not in beta-cell(Pdx1-/-) mice. Moreover, Ex-4 increased the levels of insulin and amylin mRNA transcripts and augmented glucose-stimulated insulin secretion in islets from beta-cell(Pdx1+/+) mice but not in beta-cell(Pdx1-/-) islets. Surprisingly, Ex-4 failed to reduce levels of plasma glucagon in beta-cell(Pdx1-/-) mice. These findings demonstrate that Pdx1 expression is essential for integrating GLP-1R-dependent signals regulating alpha-cell glucagon secretion and for the growth, differentiated function, and survival of islet beta-cells.
 ...
PMID:beta-Cell Pdx1 expression is essential for the glucoregulatory, proliferative, and cytoprotective actions of glucagon-like peptide-1. 1567 6

Complex gene networks are responsible for the proper operation of the endocrine pancreas. A central member of such networks, the homeodomain transcription factor Pdx1, belongs to the ParaHox gene cluster, an array of Hox-like homeobox genes. With a combination of mRNA in situ hybridisation and immunodetection, we have found that the rest of ParaHox cluster genes, Cdx1, Cdx2/3, and Cdx4, and Gsh1 and Gsh2, are all expressed in specific islet cell types of the endocrine pancreas. To our knowledge, this is the first report that locates ParaHox genes other than Pdx1 and Cdx2/3 in a place as to be involved in the pancreatic transcriptional regulatory networks, potentially regulating glucagon-insulin homeostasis.
 ...
PMID:Pdx1-related homeodomain transcription factors are distinctly expressed in mouse adult pancreatic islets. 1588 77

Pancreas development relies on a network of transcription factors belonging mainly to the Homeodomain and basic Helix-Loop-Helix families. We show in this study that, in zebrafish, sox4, a member of the SRY-like HMG-box (SOX) family, is required for proper endocrine cell differentiation. We found that two genes orthologous to mammalian Sox4 are present in zebrafish and that only one of them, sox4b, is strongly expressed in the pancreatic anlage. Transcripts of sox4b were detected in mid-trunk endoderm from the 5-somite stage, well before the onset of expression of the early pancreatic gene pdx-1. Furthermore, by fluorescent double in situ hybridization, we found that expression of sox4b is mostly restricted to precursors of the endocrine compartment. This expression is not maintained in differentiated cells although transient expression can be detected in alpha cells and some beta cells. That sox4b-expressing cells belong to the endocrine lineage is further illustrated by their absence from the pancreata of slow-muscle-omitted mutant embryos, which specifically lack all early endocrine markers while retaining expression of exocrine markers. The involvement of sox4b in cell differentiation is suggested firstly by its up-regulation in mind bomb mutant embryos displaying accelerated pancreatic cell differentiation. In addition, sox4b knock-down leads to a drastic reduction in glucagon expression, while other pancreatic markers including insulin, somatostatin, and trypsin are not significantly affected. This disruption of alpha cell differentiation is due to down-regulation of the homeobox arx gene specifically in the pancreas. Taken together, these data demonstrate that, in zebrafish, sox4b is expressed transiently during endocrine cell differentiation and plays a crucial role in the generation of alpha endocrine cells.
 ...
PMID:sox4b is a key player of pancreatic alpha cell differentiation in zebrafish. 1605 12


<< Previous 1 2 3 4 5 6 7 8 Next >>