Ginsenoside-Rb ₁ 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 (PPARγ) expression. Meanwhile, microRNA-27b (miR-27b) is also identified to regulate adipogenesis by targeting PPARγ2. In the present study, we attempted to link up the Rb ₁-promoted adipogenesis with PPARγ binding and miR-27b regulation. First, we demonstrated that GW9662, an antagonist of PPARγ, 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 PPARγ, we thus speculate that Rb ₁ may act though PPARγ to downregulate mir-27b gene transcription and mature miR-27b activity, which in turn promotes PPARγ 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.