Inhibition of c-jun N terminal kinase (JNK) improves functional beta cell mass in human islets and leads to AKT and glycogen synthase kinase-3 (GSK-3) phosphorylation

Diabetologia. 2008 Feb;51(2):298-308. doi: 10.1007/s00125-007-0889-4. Epub 2007 Dec 8.


Aims/hypothesis: Activation of c-jun N-terminal kinase (JNK) has been described in islet isolation and engraftment, making JNK a key target in islet transplantation. The objective of this study was to investigate if JNK inhibition with a cell-permeable TAT peptide inhibitor (L-JNKI) protects functional beta cell mass in human islets and affects AKT and its substrates in islet cells.

Methods: The effect of L-JNKI (10 micromol/l) on islet count, mitochondrial membrane potential, glucose-stimulated insulin release and phosphorylation of both AKT and its substrates, as well as on reversal of diabetes in immunodeficient diabetic Nu/Nu mice was studied.

Results: In vitro, L-JNKI reduced the islet loss in culture and protected from cell death caused by acute cytokine exposure. In vivo, treatment of freshly isolated human islets and diabetic Nu/Nu mice recipients of such islets resulted in improved functional beta cell mass. We showed that L-JNKI activates AKT and downregulates glycogen synthase kinase-3 beta (GSK-3B) in human islets exposed to cytokines, while other AKT substrates were unaffected, suggesting that a specific AKT/GSK-3B regulation by L-JNKI may represent one of its mechanisms of cytoprotection.

Conclusions/interpretation: In conclusion, we have demonstrated that targeting JNK in human pancreatic islets results in improved functional beta cell mass and in the regulation of AKT/GSK3B activity.

Publication types

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

MeSH terms

  • Animals
  • Cell Survival / drug effects
  • Cells, Cultured
  • Combined Modality Therapy
  • Cytokines / pharmacology
  • Diabetes Mellitus, Experimental / drug therapy
  • Diabetes Mellitus, Experimental / metabolism
  • Diabetes Mellitus, Experimental / surgery
  • Glycogen Synthase Kinase 3 / metabolism*
  • Humans
  • Insulin-Secreting Cells / cytology
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / metabolism
  • Islets of Langerhans / cytology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / metabolism
  • Islets of Langerhans Transplantation / methods
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors*
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Mice
  • Mice, Nude
  • Peptides / pharmacology*
  • Peptides / therapeutic use
  • Phosphorylation / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Transplantation, Heterologous
  • Treatment Outcome


  • Cytokines
  • L-JNKI-1
  • Peptides
  • Proto-Oncogene Proteins c-akt
  • JNK Mitogen-Activated Protein Kinases
  • Glycogen Synthase Kinase 3