The role of the PDE4D cAMP phosphodiesterase in the regulation of glucagon-like peptide-1 release

W.K. Ong, F.M. Gribble, F. Reimann, M.J. Lynch, M.D. Houslay, G.S. Baillie, B.L. Furman, N.J. Pyne

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Abstract

Increases in intracellular cyclic AMP (cAMP) augment the release/secretion of glucagon-like peptide-1 (GLP-1). As cAMP is hydrolysed by cAMP phosphodiesterases (PDEs), we determined the role of PDEs and particularly PDE4 in regulating GLP-1 release. GLP-1 release, PDE expression and activity were investigated using rats and GLUTag cells, a GLP-1-releasing cell line. The effects of rolipram, a selective PDE4 inhibitor both in vivo and in vitro and stably overexpressed catalytically inactive PDE4D5 (D556A-PDE4D5) mutant in vitro on GLP-1 release were investigated. Rolipram (1.5 mg.kg(-1) i.v.) increased plasma GLP-1 concentrations approximately twofold above controls in anaesthetized rats and enhanced glucose-induced GLP-1 release in GLUTag cells (EC50 similar to 1.2 nmol.L-1). PDE4D mRNA transcript and protein were detected in GLUTag cells using RT-PCR with gene-specific primers and Western blotting with a specific PDE4D antibody respectively. Moreover, significant PDE activity was inhibited by rolipram in GLUTag cells. A GLUTag cell clone (C1) stably overexpressing the D556A-PDE4D5 mutant, exhibited elevated intracellular cAMP levels and increased basal and glucose-induced GLP-1 release compared with vector-transfected control cells. A role for intracellular cAMP/PKA in enhancing GLP-1 release in response to overexpression of D556A-PDE4D5 mutant was demonstrated by the finding that the PKA inhibitor H89 reduced both basal and glucose-induced GLP-1 release by 37% and 39%, respectively, from C1 GLUTag cells. PDE4D may play an important role in regulating intracellular cAMP linked to the regulation of GLP-1 release.
Original languageEnglish
Pages (from-to)633-644
Number of pages11
JournalBritish Journal of Pharmacology
Volume157
Issue number4
DOIs
Publication statusPublished - Jun 2009

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Keywords

  • cAMP
  • dominant negative
  • glucagon-like peptide-1
  • GLUTag cells
  • H89
  • PDE4D4
  • phosphodiesterase
  • rolipram

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