Mechanisms of action of rosiglitazone in the protection of pancreatic beta cells from free fatty acid induced damage

A wealth of recent evidence implicates increasing obesity levels in the rising global epidemic of type 2 diabetes. At a cellular level, high fatty acid concentrations contribute to increasing p-cell dysfunction and eventual p-cell failure. We have shown that the thiazolidinedione (TZD) rosiglitazone has direct effects on pancreatic p-cell function. The aim of this study was to determine the cell signalling molecules mediating these effects, and to test the hypothesis that rosiglitazone can protect pancreatic p-cells from the detrimental effects of free fatty acids. Utilising the mouse p-cell line MIN6, MTT assays showed that at 5 mM glucose concentrations, addition of 0.4 mM palmitate for 72 hours resulted in a 60% loss of MIN6 cell viability (P<O.O 1). However, the presence of 10 p M rosiglitazone completely abolished the effect of palmitate. To determine the cell signalling pathways involved, MIN6 cells were stimulated with 10 u M rosiglitazone for 2 hours and whole cell extracts analysed. Western blot analysis indicated that total levels of the stress activated p38 MAPK were reduced by over 50% (P<0.05) in the presence of rosiglitazone. Rosiglitazone stimulated phosphorylation of ACC (P<O.Ol), an effect inhibited by compound C, indicating that rosiglitazone activates AMPK in MIN6 cells over 2 hours. Finally, casein kinase 2 (CK2) activity assays indicated that rosiglitazone stimulates a 3-fold increase in CK2 activity (P