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

ETHNOPHARMACOLOGICAL RELEVANCE

Cinnamomum osmophloeum is used for various ethnomedical conditions in Taiwan including diabetic complications.

AIM OF THE STUDY

The 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 METHODS

Silica 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)-beta and glucose transporter 4 (GLUT4) in differentiated mouse 3T3-L1 adipocytes, and the results were compared with the reference drug insulin.

RESULTS

The compound CO-1 at a concentration of 5 microM 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 microM tested. Furthermore, 5 microM of CO-1 and 20 microM of CO-2 showed potential to increase the phosphorylation of IRbeta 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.

CONCLUSION

The 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.