Glucagon-like peptide-1 increases beta-cell glucose competence and proliferation by translational induction of insulin-like growth factor-1 receptor expression

J Biol Chem. 2010 Apr 2;285(14):10538-45. doi: 10.1074/jbc.M109.091116. Epub 2010 Feb 9.

Abstract

Glucagon-like peptide-1 (GLP-1) protects beta-cells against apoptosis, increases their glucose competence, and induces their proliferation. We previously demonstrated that the anti-apoptotic effect was mediated by an increase in insulin-like growth factor-1 receptor (IGF-1R) expression and signaling, which was dependent on autocrine secretion of insulin-like growth factor 2 (IGF-2). Here, we further investigated how GLP-1 induces IGF-1R expression and whether the IGF-2/IGF-1R autocrine loop is also involved in mediating GLP-1-increase in glucose competence and proliferation. We show that GLP-1 up-regulated IGF-1R expression by a protein kinase A-dependent translational control mechanism, whereas isobutylmethylxanthine, which led to higher intracellular accumulation of cAMP than GLP-1, increased both IGF-1R transcription and translation. We then demonstrated, using MIN6 cells and primary islets, that the glucose competence of these cells was dependent on the level of IGF-1R expression and on IGF-2 secretion. We showed that GLP-1-induced primary beta-cell proliferation was suppressed by Igf-1r gene inactivation and by IGF-2 immunoneutralization or knockdown. Together our data show that regulation of beta-cell number and function by GLP-1 depends on the cAMP/protein kinase A mediated-induction of IGF-1R expression and the increased activity of an IGF-2/IGF-1R autocrine loop.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Animals
  • Apoptosis
  • Blotting, Western
  • Cell Proliferation
  • Cells, Cultured
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Fluorescent Antibody Technique
  • Glucagon-Like Peptide 1 / pharmacology*
  • Glucose / metabolism*
  • Insulin-Like Growth Factor II / genetics
  • Insulin-Like Growth Factor II / metabolism
  • Insulin-Secreting Cells / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Protein Biosynthesis*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptor, IGF Type 1 / genetics*
  • Receptor, IGF Type 1 / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Transcription, Genetic

Substances

  • RNA, Messenger
  • Insulin-Like Growth Factor II
  • Glucagon-Like Peptide 1
  • Cyclic AMP
  • Receptor, IGF Type 1
  • Cyclic AMP-Dependent Protein Kinases
  • Glucose
  • 1-Methyl-3-isobutylxanthine