Characterisation of a protein kinase B inhibitor in vitro and in insulin treated liver cells

Objective: Abnormal expression of the hepatic gluconeogenic genes (glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK)) contributes to hyperglycemia. These genes are repressed by insulin but this process is defective in diabetes. Protein kinase B (PKB) is implicated in this action of insulin. An inhibitor of PKB, termed Akti-1/2, was recently reported, however the specificity and efficacy against insulin induced PKB was not reported. Our aim was to characterise the specificity and efficacy of Akti-1/2 in cells exposed to insulin and then establish whether inhibition of PKB is sufficient to prevent regulation of hepatic gene expression by insulin. Design: Akti-1/2 was assayed against seventy kinases in vitro, and its ability to block PKB activation in cells exposed to insulin fully characterised.