Kr-pok increases gluconeogenesis through upregulation of G6pc and Pck1

Abstract

Gluconeogenesis is essential for maintenance of blood glucose level during fasting. Gluconeogenesis is tightly regulated by the key enzymes, including glucose-6-phophatase (G6pc) and phosphoenolpyruvate carboxykinase (PEPCK). Transcription of the genes encoding the two enzymes is tightly regulated under fasting condition. Kr-pok knockout mice showed a decrease in blood glucose level. Differential gene expression analysis of Kr-pok wild type and knockout mice liver showed that mRNA of G6pc and Pck1 are decreased. I investigated the role of Kr-pok in the regulation of gluconeogenesis. I found that Kr-pok is induced in the liver of fasted mice. Also, forskolin treatment increased Kr-pok expression in mice primary hepatocytes and knockout of Kr-pok decreased transcription of G6pc and Pck1. These results showed that, under fasting condition, Kr-pok can increase expression of G6pc and Pck1genes. I investigated how Kr-pok can increase transcription of G6pc and Pck1 genes. Transient transcription assays of the reporter plasmid showed that Kr-pok increases transcription by acting on the IRSs of the G6pc and Pck1 promoters. ChIP assays revealed that Kr-pok reduces acetylation of FoxO1 and thereby increases FoxO1 binding to the IRS elements of the promoters to activate transcription of G6pc and Pck1. Kr-pok increased the interaction between FoxO1 and HDAC3 and deacetylated FoxO1. Also, I found that protein stability of Kr-pok is increased by treatment of forskolin. These results suggested that Kr-pok might be a metabolic regulator controlling expression of the two key gluconeogenic enzymes, G6pc and PEPCK.