The mechanism and role of intracellular α-ketoglutarate reduction in hepatic stellate cell activation

Background: The activation of hepatic stellate cells (HSCs) plays a central role in liver fibrosis. alpha-ketoglutarate is a natural metabolite and previous studies have shown that increase in intracellular alpha-ketoglutarate can inhibit HSC activation. Aim: The aim of the present study is to determine the changes and role of intracellular alpha-ketoglutarate in HSC activation and clarify its mechanism of action. Methods: A human HSC cell line (LX-2) and the primary mouse HSC were used in the present study. We detected the changes of intracellular alpha-ketoglutarate levels and the expression of enzymes involved in the metabolic processes during HSC activation. We used siRNA to determine the role of intracellular alpha-ketoglutarate in HSC activation and elucidate the mechanism of the metabolic changes. Results: Our results demonstrated that intracellular alpha-ketoglutarate levels decreased with an HSC cell line and primary mouse HSC activation, as well as the expression of isocitrate dehydrogenase 2 (IDH2), an enzyme that catalyzes the production of alpha-ketoglutarate. In addition, knockdown of IDH2 efficiently promoted the activation of HSCs, which was able to be reversed by introduction of an alpha-ketoglutarate analogue. Furthermore, we demonstrated that alpha-ketoglutarate regulated HSC activation is independent of transforming growth factor-beta 1 (TGF-beta 1). Conclusions: Our findings demonstrated that decrease in IDH2 expression limits the production of alpha-ketoglutarate during HSC activation and in turn promotes the activation of HSCs through a TGF-beta 1 independent pathway. The present study suggests that IDH2 and alpha-ketoglutarate may be potential new targets for the prevention and treatment of liver fibrosis.