miR-375 targets 3'-phosphoinositide-dependent protein kinase-1 and regulates glucose-induced biological responses in pancreatic beta-cells

Abdelfattah El Ouaamari, Nadine Baroukh, Geert A Martens, Patricia Lebrun, Daniel Pipeleers, Emmanuel van Obberghen

Research output: Contribution to journalArticle

Abstract

OBJECTIVE: MicroRNAs are short, noncoding RNAs that regulate gene expression. We hypothesized that the phosphatidylinositol 3-kinase (PI 3-kinase) cascade known to be important in beta-cell physiology could be regulated by microRNAs. Here, we focused on the pancreas-specific miR-375 as a potential regulator of its predicted target 3'-phosphoinositide-dependent protein kinase-1 (PDK1), and we analyzed its implication in the response of insulin-producing cells to elevation of glucose levels.

RESEARCH DESIGN AND METHODS: We used insulinoma-1E cells to analyze the effects of miR-375 on PDK1 protein level and downstream signaling using Western blotting, glucose-induced insulin gene expression using quantitative RT-PCR, and DNA synthesis by measuring thymidine incorporation. Moreover, we analyzed the effect of glucose on miR-375 expression in both INS-1E cells and primary rat islets. Finally, miR-375 expression in isolated islets was analyzed in diabetic Goto-Kakizaki (GK) rats.

RESULTS: We found that miR-375 directly targets PDK1 and reduces its protein level, resulting in decreased glucose-stimulatory action on insulin gene expression and DNA synthesis. Furthermore, glucose leads to a decrease in miR-375 precursor level and a concomitant increase in PDK1 protein. Importantly, regulation of miR-375 expression by glucose occurs in primary rat islets as well. Finally, miR-375 expression was found to be decreased in fed diabetic GK rat islets.

CONCLUSIONS: Our findings provide evidence for a role of a pancreatic-specific microRNA, miR-375, in the regulation of PDK1, a key molecule in PI 3-kinase signaling in pancreatic beta-cells. The effects of glucose on miR-375 are compatible with the idea that miR-375 is involved in glucose regulation of insulin gene expression and beta-cell growth.

Original languageEnglish
Pages (from-to)2708-2717
Number of pages10
JournalDiabetes
Volume57
Issue number10
DOIs
Publication statusPublished - 2008

Keywords

  • 3' Untranslated Regions/genetics
  • 3-Phosphoinositide-Dependent Protein Kinases
  • Animals
  • Base Sequence
  • Blotting, Western
  • Cell Proliferation/drug effects
  • Cell Survival/drug effects
  • Cells, Cultured
  • Gene Expression/drug effects
  • Glucose/pharmacology
  • Insulin/pharmacology
  • Insulin-Secreting Cells/cytology
  • Male
  • MicroRNAs/genetics
  • Oligonucleotides, Antisense/pharmacology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases/genetics
  • RNA, Messenger/genetics
  • Rats
  • Rats, Wistar
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction/drug effects

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