Transcriptional profiling reveals functional links between RasGrf1 and Pttg1 in pancreatic beta cells
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE56371 | GEO | 2014/12/01
SECONDARY ACCESSION(S): PRJNA243059
REPOSITORIES: GEO
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Project description:Peroxisome proliferator-activated receptor beta/delta protects against obesity by reducing dyslipidemia and insulin resistance via effects in various organs, including muscle, adipose tissue, liver, and heart. However, nothing is known about the function of PPAR-beta in pancreas, a prime organ in the control of glucose metabolism. To gain insight into so far hypothetical functions of this PPAR isotype in insulin production, we specifically ablated Ppar-beta in pancreas. The mutated mice developed a chronic hyperinsulinemia, due to an increase in both beta-cell mass and insulin secretion. Gene expression profiling indicated a broad repressive function of PPAR-beta impacting the vesicular compartment, actin cytoskeleton, and metabolism of glucose and fatty acids. Analyses of insulin release from the islets revealed an increased second-phase glucose-stimulated insulin secretion. Higher levels of PKD, PKC-delta and diacyglycerol in mutated animals lead to an enhanced formation of trans-Golgi network (TGN)-to-plasma-membrane transport carriers in concert with F-actin disassembly, which resulted in increased insulin secretion and its associated systemic effects. Taken together, these results provide evidence for PPAR-beta playing a repressive role on beta-cell growth and insulin exocytosis, which shed new light on its anti-obesity action. Pancreas-specific knock-out animals were generated by breeding mice harbouring a floxed Ppar-beta (PPARbetafl/fl) to mice expressing the Cre transgene under the control of the Pdx1 promoter (Pdx1Cre). Islets from 3 different animals from the knock-out group Pdx1Cre;PPARbetafl/fl and the control littermates group PPARbetafl/fl were compared.
2012-08-30 | E-GEOD-16048 | biostudies-arrayexpress
Project description:Aims: establishment of reference samples to investigate gene expression selective for endocrine or ductal-exocrine cells within the adult human pancreas. To this end, human islet endocrine cells, FACS-enriched in insulin+ cells, (n=3) and human exocrine ductal cells (n=2) are compared on Affymetrix HG133A platform with duplicate hybridizations of a panel of other primary human tissues. The microarray analysis was performed on 3 pools of human beta cell-enriched cell fractions, isolated from 10 non-selected donor organs, and 2 pools of duct cell-enriched fractions obtained from 6 non-selected donor pancreases. The cells were suspension-cultured for 2-3 weeks along standard procedures and with no specific treatment prior to FACS-sorting and RNA extraction. The average composition of human beta cell-preparations was 55 ± 13% insulin+ cells, 13±8% glucagon+ cells and 21 ±7% non-granulated cells. Pancreatic duct cells-enriched preparations contained 85 ±7% cytokeratin 19+ cells with 4 ± 1% insulin+ cells and 6 ±4% glucagon+ cells and were isolated as described by Heimberg H. et al.( Diabetes 2001,49: 571-579 ). Pancreatic cell mRNA profiles were compared to those of a panel of other human primary tissues (n=2 biological replicates). This dataset is part of the TransQST collection.
2011-07-21 | E-GEOD-30803 | biostudies-arrayexpress
Project description:ABSTRACT Background: The control of the functional pancreatic b-cell mass serves the key homeostatic function of releasing the right amount of insulin to keep blood sugar in the normal range. It is not fully understood though how b-cell mass is determined. Methodology/principal findings: Conditional chicken ovalbumin upstream promoter transcription factor II (COUP-TFII)-deficient mice were generated and crossed with mice expressing Cre under the control of pancreatic duodenal homeobox 1 (pdx1) gene promoter. Ablation of COUP-TFII in pancreas resulted in glucose intolerance. Beta-cell number was reduced at 1 day and 3 weeks postnatal. Together with a reduced number of insulin-containing cells in the ductal epithelium and normal b-cell proliferation and apoptosis, this suggests decreased b-cell differentiation in the neonatal period. By testing islets isolated from these mice and cultured b-cells with loss and gain of COUP-TFII function, we found that COUP-TFII induces the expression of the b-catenin gene and its target genes such as cyclin D1 and axin 2. Moreover, induction of these genes by glucagon-like peptide 1 (GLP-1) via b-catenin was impaired in absence of COUP-TFII. The expression of two other target genes of GLP-1 signaling, GLP-1R and PDX-1 was significantly lower in mutant islets compared to control islets, possibly contributing to reduced b-cell mass. Finally, we demonstrated that COUP-TFII expression was activated by the Wnt signaling-associated transcription factor TCF7L2 (T-cell factor 7-like 2) in human islets and rat b-cells providing a feedback loop. Conclusions/significance: Our findings show that COUP-TFII is a novel component of the GLP-1 signaling cascade that increases b-cell number during the neonatal period. COUP-TFII is required for GLP-1 activation of the b-catenin-dependent pathwayand its expression is under the control of TCF7L2.
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