Inhibition of SphK2 Stimulated Hepatic Gluconeogenesis Associated with Dephosphorylation and Deacetylation of STAT3

Abstract

Background: Sphingosine kinase (SphK) is considered as a potential target for developing novel therapeutics of cancer and other diseases including diabetes. As the major SphK isoform in the liver, much less is known the role of SphK2 involved in regulating hepatic glucose metabolism.

Method: In this study, RNA interference, real time RT-PCR, western blot and immunoprecipitation method was used to investigate the regulation of SphK2 in hepatic glucose metabolism.

Results: Both siRNA and SphK2 inhibitor ABC294640 stimulated expression of gluconeogenetic gene PEPCK and G6Pase but not enzymes of hepatic glycogenolysis, glycolysis and glycogen synthesis. Inhibition of SphK2 also prevented insulin repressed PEPCK and G6Pase expression as well as glucose production levels. Furtherly, inhibition of SphK2 inactivated STAT3 by decreasing both phosphorylation on Tyr705 and acetylation on lysine residue, and led to stimulation of PEPCK and G6Pase expression. Inhibition of SphK2 also prevented IL-6 dependent activation of STAT3 and suppression of PEPCK and G6pase expression both in vitro and in vivo.

Conclusion: Our study suggests that SphK2 participates in hepatic glucose metabolism related to activation of STAT3.

Keywords: Acetylation; Gluconeogenesis; Phosphorylation; STAT3; SphK2.