Putative identification of components in Zengye Decoction and their effects on glucose consumption and lipogenesis in insulin-induced insulin-resistant HepG2 cells

Zengye Decoction (ZYD) is a well-known traditional medicine in China used for treating diseases associated with “Yin deficiency” such as diabetes. However, little information is available on its components, pharmacological effects and underlying mechanisms. This study was designed to identify its active components and evaluate the effects and mechanisms of ZYD on glucose consumption and lipogenesis in insulin-induced insulin-resistant (IR)-HepG2 cells. In this study, 45 compounds of ZYD were putatively identified, in which the iridoid glycosides such as catalpol, aucubin and harpagide were identified as the main components. The insulin-resistant (IR)-HepG2 cell model was established and the effect of ZYD at three doses (0.17, 0.5 and 1.5 μg/mL) on cell growth was evaluated with an IncuCyte™ live-cell imaging system. The effects of ZYD on glucose consumption and uptake were evaluated by glucose consumption and uptake assay. Meanwhile, the effect of ZYD on lipogenesis was investigated in IR-HepG2 cells by oil red O (ORO) staining. Western blot was applied to observe the changes in some of the key factors involved in glucose metabolism and lipogenesis. It was found that the ZYD at a dose of 1.5 μg/mL exhibited an inhibitory activity on IR-HepG2 cell growth. Besides, ZYD at doses of 0.5 and 1.5 μg/mL accelerated the glucose consumption, glucose uptake and reduced the lipogenesis in the IR-HepG2 cells. Western blot studies revealed that ZYD phosphorylated AMP-activated protein kinase α subunits (AMPKα), upregulated hexokinase (HK), phosphorylated acetyl-CoA carboxylase alpha (pACC1) and carnitine palmitoyltransferase 1A (CPT1A) in the IR-HepG2 cells. These results indicate ZYD promotes glucose consumption and uptake, and attenuates lipogenesis in IR-HepG2 cells, which may be involved in activating AMPK and regulating its downstream factors including HK, pACC1 and CPT1A.