Sennidin stimulates glucose incorporation in rat adipocytes

A novel small molecule compound which exerts insulin mimetic is desirable. Dozens of natural products that have quinone, naphthoquinone, or anthraquinone structure, were tested by a glucose incorporation assay. We found that sennidin A, anthraquinone derivative, stimulated glucose incorporation to near level of maximal insulin-stimulated and sennidin B, a stereoisomer of sennidin A, also stimulated, but the activity of sennidin B was lower than sennidin A. Sennidin A-stimulated glucose incorporation was completely inhibited by wortmannin. Sennidin A did not induce tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS-1), but induced phosphorylation of Akt and glucose transporter 4 (GLUT4) translocation. Our results suggest that in rat adipocytes, sennidin A stimulates glucose incorporation in the phosphatidylinositol 3-kinase (PI3K)- and Akt-dependent, but in the IR/IRS1-independent manner.