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Early peroxisome proliferator-activated receptor gamma regulated genes involved in expansion of pancreatic beta cell mass.


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Authors

Vivas, Yurena 
Martínez-García, Cristina 
Izquierdo, Adriana 
Garcia-Garcia, Francisco 
Callejas, Sergio 

Abstract

BACKGROUND: The progression towards type 2 diabetes depends on the allostatic response of pancreatic beta cells to synthesise and secrete enough insulin to compensate for insulin resistance. The endocrine pancreas is a plastic tissue able to expand or regress in response to the requirements imposed by physiological and pathophysiological states associated to insulin resistance such as pregnancy, obesity or ageing, but the mechanisms mediating beta cell mass expansion in these scenarios are not well defined. We have recently shown that ob/ob mice with genetic ablation of PPARγ2, a mouse model known as the POKO mouse failed to expand its beta cell mass. This phenotype contrasted with the appropriate expansion of the beta cell mass observed in their obese littermate ob/ob mice. Thus, comparison of these models islets particularly at early ages could provide some new insights on early PPARγ dependent transcriptional responses involved in the process of beta cell mass expansion RESULTS: Here we have investigated PPARγ dependent transcriptional responses occurring during the early stages of beta cell adaptation to insulin resistance in wild type, ob/ob, PPARγ2 KO and POKO mice. We have identified genes known to regulate both the rate of proliferation and the survival signals of beta cells. Moreover we have also identified new pathways induced in ob/ob islets that remained unchanged in POKO islets, suggesting an important role for PPARγ in maintenance/activation of mechanisms essential for the continued function of the beta cell. CONCLUSIONS: Our data suggest that the expansion of beta cell mass observed in ob/ob islets is associated with the activation of an immune response that fails to occur in POKO islets. We have also indentified other PPARγ dependent differentially regulated pathways including cholesterol biosynthesis, apoptosis through TGF-β signaling and decreased oxidative phosphorylation.

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Keywords

Animals, Cell Proliferation, Cell Survival, Cholesterol, Down-Regulation, Female, Gene Expression Regulation, Gene Knockout Techniques, Insulin Resistance, Insulin-Secreting Cells, Mice, Obesity, Oxidation-Reduction, PPAR gamma, Phosphorylation, Signal Transduction, Transcription, Genetic, Transforming Growth Factor beta

Journal Title

BMC Med Genomics

Conference Name

Journal ISSN

1755-8794
1755-8794

Volume Title

Publisher

Springer Science and Business Media LLC
Sponsorship
Medical Research Council (G0802051)
Medical Research Council (G0600717)