Autocrine insulin action activates Akt and increases survival of isolated human islets
Autor: | Mauro Castellarin, Dusica Maysinger, Stephen C. Hanley, Reid Aikin, Mark Lipsett, Steven Paraskevas, Lawrence Rosenberg |
---|---|
Rok vydání: | 2006 |
Předmět: |
endocrine system
medicine.medical_specialty Programmed cell death Cell Survival Endocrinology Diabetes and Metabolism medicine.medical_treatment Biology chemistry.chemical_compound Islets of Langerhans Internal medicine Internal Medicine medicine Cadaver Humans Insulin Phosphatidylinositol Phosphorylation Autocrine signalling Protein kinase B Pancreas PI3K/AKT/mTOR pathway Cells Cultured Organ Size Middle Aged Cell biology Mitochondria Transplantation Enzyme Activation Kinetics Endocrinology chemistry Apoptosis Culture Media Conditioned Proto-Oncogene Proteins c-akt |
Zdroj: | Diabetologia. 49(12) |
ISSN: | 0012-186X |
Popis: | The phosphatidylinositol 3-kinase (PI3K)/Akt pathway plays a critical role in promoting the survival of pancreatic beta cells. Akt becomes activated in isolated human islets following overnight culture despite significant levels of cell death. The aim of the current study was to identify the cause of the observed increase in Akt phosphorylation in isolated islets. We hypothesised that a factor secreted by the islets in culture was acting in an autocrine manner to activate Akt.In order to identify the stimulus of the PI3K/Akt pathway in culture, we examined the effects of different culture conditions on Akt phosphorylation and islet survival during the immediate post-isolation period.We demonstrated that islet-conditioned medium induced Akt phosphorylation in freshly isolated human islets, whereas frequent medium replacement decreased Akt phosphorylation. Following overnight culture, islet-conditioned medium contained significantly elevated levels of insulin, indicating that insulin may be responsible for the observed increase in Akt phosphorylation. Indeed, treatment with an anti-insulin antibody or with inhibitors of insulin receptor/IGF receptor 1 kinase activity suppressed Akt phosphorylation, leading to decreased islet survival. In addition, dispersion of islets into single cells also suppressed Akt phosphorylation and induced islet cell death, indicating that islet integrity is also required for maximal Akt phosphorylation.Our findings demonstrate that insulin acts in an autocrine manner to activate Akt and mediate the survival of isolated human islets. These findings provide new information on how culturing islets prior to transplantation may be beneficial to their survival by allowing for autocrine activation of the pro-survival Akt pathway. |
Databáze: | OpenAIRE |
Externí odkaz: |