INSULINOMIMETIC EFFECTS OF MYRICETIN ON LIPOGENESIS AND GLUCOSE-TRANSPORT IN RAT ADIPOCYTES BUT NOT GLUCOSE-TRANSPORTER TRANSLOCATION

Myricetin is a naturally occurring flavonol that is commonly found in tea, berries, fruits, and medicinal plants. It mimics insulin in stimu lating lipogenesis and glucose transport in rat adipocytes in vitro. I t was found to stimulate lipogenesis in rat adipocytes and enhance the stimulatory effect of insulin. The EC(50) was estimated to be about 6 5 mu M. Myricetin did not have any effect on insulin receptor autophos phorylation nor on the tyrosine kinase activity of the receptor. Howev er, myricetin stimulated both D-glucose and D-3-O-methyl-glucose uptak e in rat adipocytes. The V-max of glucose transport was increased, but the K-m did not change significantly. Immunoblot analysis of Glut4 in rat adipocyte plasma membrane showed that the stimulation of glucose transport was not a consequence of glucose transporter translocation. Instead, the stimulation in glucose uptake probably was due to a chang e in the intrinsic activity of the glucose transporter possibly caused by alterations in membrane fluidity or transporter-lipid interactions as a result of the insertion of myricetin into the membrane bilayer. Thus, myricetin may have therapeutic potential in the management of no n-insulin-deendent diabetes mellitus by stimulating glucose uptake wit hout the presence of fully functional insulin receptors.