Effect of flavonol glycosides from Cinnamomum osmophloeum leaves on adiponectin secretion and phosphorylation of insulin receptor-β in 3T3-L1 adipocytes

Ethnopharmacological relevanceCinnamomum osmophloeum is used for various ethnomedical conditions in Taiwan including diabetic complications.Aim of the studyThe aim of present study was to identify the anti-diabetic compounds from C. osmophloeum leaves and evaluate the preliminary molecular basis for their insulin-like effects.Materials and methodsSilica gel column chromatographic purification of MeOH extract from leaves of C. osmophloeum resulted in the isolation of a two kaempferol glycosides CO-1 and CO-2. These two compounds were evaluated for their effects on adiponectin secretion, tyrosine phosphorylation of insulin receptor (IR)-β and glucose transporter 4 (GLUT4) in differentiated mouse 3T3-L1 adipocytes, and the results were compared with the reference drug insulin.ResultsThe compound CO-1 at a concentration of 5 μM was able to act as an insulin-mimetic in terms of its ability to increase adiponectin secretion by 12.2-fold, while CO-2 has no such effect up to 20 μM tested. Furthermore, 5 μM of CO-1 and 20 μM of CO-2 showed potential to increase the phosphorylation of IRβ by 2.3- and 2.1-fold, respectively, in addition to their positive effect on GLUT4 translocation. CO-1 and CO-2 stimulated GLUT4 translocation are reduced by phosphatidylinositol-3-kinase (PI3-K) inhibitor.ConclusionThe present study indicates that the insulin-like anti-diabetic mechanism of constituents from C. osmophloeum leaves in part due to enhanced adiponectin secretion, and activation of insulin signaling pathway leading to GLUT4 translocation which involved phosphorylation of IR and activation of PI3-K.