Ginsenoside Rb3 strengthens the hypoglycemic effect through AMPK for inhibition of hepatic gluconeogenesis

Abstract

Ginsenoside Rb3 is one of the major active components in protopanaxdiol type ginsenosides, and has demonstrated anti-diabetic activity. However, the mechanism of this action has yet to be elucidated. The present study investigated the effects of ginsenoside Rb3 on the AMP-activated protein kinase (AMPK) gluconeogenesis pathway. The present study involved the use of HepG2 cells and western blot analysis to systematically evaluate the effect of ginsenoside Rb3 on AMPK signaling proteins and key factors of gluconeogenesis [phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase, forkhead transcription factor 1 (FOXO1) and hepatic nuclear receptor 4α (HNF4α)]. The results indicated that 25 µM ginsenoside Rb3 significantly activated AMPK activity, increased the ratio of p-AMPK/total-AMPK, and had synergistic effects with the activator of AICAR on the activation of AMPK. Further analysis indicated that the expression of the transcription factor FOXO1 and HNF4α protein, two important factors in the pathway of HepG2 cell gluconeogenesis, was significantly suppressed by ginsenoside Rb3. PEPCK and G6Pase were subsequently inhibited, which led to the suppression of gluconeogenesis. These effects were partially blocked by the AMPK inhibitor, Compound C, which indicated that the inhibition effects of ginsenoside Rb3 on hepatic gluconeogenesis were predominantly due to the activation of the AMPK signaling pathway. These data suggested that ginsenoside Rb3 can suppress hepatic gluconeogenesis, at least partially through stimulation of AMPK activity.