Simvastatin induces activation of the serine-threonine protein kinase AKT and increases survival of isolated human pancreatic islets.
BACKGROUND
Pancreatic islets are susceptible to myriad insults that occur during islet isolation and transplantation. Studies demonstrated the role of Akt in regulating pancreatic beta-cell growth and survival. Activation of Akt maintains Bad phosphorylation and prevents its binding to mitochondrial targets, decreases caspase-9 activity, and prevents the translocation of forkhead transcription factors (FKHR). Simvastatin activates Akt in mammalian cells; therefore, we investigated the role of simvastatin on human pancreatic islets (HPI) survival.


METHODS
HPI were treated with simvastatin, with and without LY294002, an inhibitor of phosphoinositide 3-kinase. PI viability was examined with ethidium bromide-acridine orange, and apoptosis was examined using a quantitative assay. Akt, Bad, FKHR phosphorylation, and mitochondrial cytochrome release were analyzed by Western blots. Caspase-9 activity was assessed by a fluorometric assay. A limited number of HPI were transplanted after simvastatin treatment in diabetic NOD-SCID mice.


RESULTS
Low levels of Akt phosphorylation (activation) were demonstrated early after islet isolation. Akt activation; increase in islet viability; and decrease in Bad phosphorylation, cytochrome release, caspase-9 activation, and translocation of FKHR were observed after simvastatin treatment, effects reversed by LY294002. Among recipients of islets without simvastatin, none demonstrated reversal of diabetes after the transplant. In contrast, 58% of the recipients given islets treated with simvastatin remained euglycemic 30 days after the transplant.


CONCLUSIONS
Targeting the survival pathway with simvastatin exerts a cytoprotective effect on isolated PI. Activation of the Akt pathway is a potential new therapeutic approach to reduce loss of functional islet mass to bolster success in clinical islet transplantation.
Contreras
Juan L
JL
Transplant Center, Division of Transplantation, University of Alabama at Birmingham, 748 Lyons-Harrison Research Building, 701 19th Street South, Birmingham, AL 35294, USA. juan.contreras@ccc.uab.edu.
Smyth
Cheryl A
CA
Bilbao
Guadalupe
G
Young
Carlton J
CJ
Thompson
J Anthony
JA
Eckhoff
Devin E
DE
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D003922:Diabetes Mellitus, Type 1 / Q000628:therapy; D053222:Fas Ligand Protein; D051858:Forkhead Transcription Factors; D015870:Gene Expression; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D016381:Islets of Langerhans Transplantation; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008928:Mitochondria / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019821:Simvastatin / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism; D051025:bcl-Associated Death Protein
D002352:Carrier Proteins; D053453:Caspase 9; D020169:Caspases; D003574:Cytochrome c Group; D053222:Fas Ligand Protein; D051858:Forkhead Transcription Factors; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019821:Simvastatin; D014157:Transcription Factors; D051025:bcl-Associated Death Protein; C494819:BAD protein, human; C494820:Bad protein, mouse; C505661:FASLG protein, human; C505658:Fasl protein, mouse; C494918:AKT1 protein, human; C506433:CASP9 protein, human; C506434:Casp9 protein, mouse