Ginsenoside-Rb1 Promotes Adipogenesis Through Regulation of PPARγ and MicroRNA-27b

Ginsenoside-Rb-1 (Rb-1), one of the bioactive components in ginseng extract, is recently reported to be able to promote adipogenesis and peroxisome proliferator-activated receptor gamma (PPAR gamma) expression. Meanwhile, microRNA-27b (miR-27b) is also identified to regulate adipogenesis by targeting PPAR gamma 2. In the present study, we attempted to link up the Rb-1-promoted adipogenesis with PPAR gamma binding and miR-27b regulation. First, we demonstrated that GW9662, an antagonist of PPAR gamma, could block Rb-1-induced 3T3-L1 differentiation with little toxicity towards cell proliferation. Then, expression levels for both of miR-27b and its primary transcript, pri-mir-27b, were found to decrease upon Rb-1 treatment. Again, GW9662 could attenuate the inhibitory effect of Rb-1 on both miR-27 and pri-mir-27b expression. Since Rb-1 was demonstrated to have binding activity towards PPAR gamma, we thus speculate that Rb-1 may act though PPAR gamma to downregulate mir-27b gene transcription and mature miR-27b activity, which in turn promotes PPAR gamma expression and adipogenesis. Enhancement on adipogenesis of adipose tissues is expected to prevent lipotoxicty in nonadipose tissues. Our data may give a better illustration to explain the antidiabetic effect of Rb-1 and provide a hint on treatment of lipid related metabolic diseases in the future.