Ginsenoside Rb2 promotes glucose metabolism and attenuates fat accumulation via AKT-dependent mechanisms

Abstract

Ginsenosides, the major active constituents of ginseng, have been demonstrated possess anti-diabetic, anti-inflammatory effects. Ginsenoside Rb2 (Rb2) is the most abundant saponin in Panax ginseng, this study investigates the role of Rb2 in the anti-hyperglycemic mechanism of insulin-sensitive cell lines 3T3-L1 adipocytes as well as high fat diet-induced obesity mice. Glucose uptake of 3T3-L1 adipocytes was measured. The insulin signaling cascade, including insulin AKT, insulin receptor (IR) beta-subunit, IR substrate (IRS) -1, phosphatidylinositol 3-kinase (PI3K) were also examined. TNF-α-treated 3T3-L1 adipocytes were used as an insulin resistant model in which p-AKT, c-Jun NH2-terminal kinase (JNK), MAPK, and nuclear factor (NF) -κB signaling cascades were examined. As an in vivo study, C57BL/6J mice were fed with a high-fat diet for 9 weeks, with or without Rb2 supplementation. Then we investigated the effects of Rb2 on glycometabolism in these high fat diet-induced obesity mice. Our results demonstrate Rb2 increases glucose uptake in 3T3-L1 adipocytes, independent of insulin receptor β-subunit (IRβ) and principally through the insulin receptor substrate (IRS)-1-phosphatidylinositol 3-kinase (PI3K)-AKT/PKB pathway. Rb2 inhibited TNF-α-induced activation of MAPK and nuclear factor (NF)-κB signaling pathway as well as the expression of inflammatory factors. In high fat diet-induced obesity mice, Rb2 attenuated fat mass and regulated insulin resistance. In mouse adipose tissue, Rb2 phosphorylation of AKT was correlated with glycometabolism. Furthermore, Rb2 attenuates insulin resistance in 3T3-L1 adipocytes, reduces fat mass, and improves insulin sensitivity in high fat diet-obesity mice.