Epigallocatechin Gallate Inhibits Endothelin‐1 Stimulation of 3T3‐L1 Adipocyte Glucose Uptake

Abstract

ObjectiveThis study was designed to investigate whether epigallocatechin gallate (EGCG) modulated the acute (30 min) and chronic (6 h) effects of endothelin (ET)‐1 on glucose uptake and glucose transporters in 3T3‐L1 adipocytes.MethodsGlucose uptake was assayed to measure the uptake of 3H‐2‐deoxyglucose. Western blot analysis was performed to measure levels of Gluts and ET‐1 signaling molecules.ResultsEGCG at 10 μM for 2 h was found to inhibit the acute effects of ET‐1 on glucose uptake and the translocation of glucose transporter (Glut)‐4 from the cytosol to the plasma membrane. EGCG had no effects on the translocation of Glut1 and total levels of Glut‐1 and Glut‐4 proteins. But, we observed that EGCG prevented the chronically ET‐1‐increased levels of glucose uptake and Glut‐1 protein expression, and it had no effects on the ET‐1‐altered levels of Glut‐1 and Glut‐4 translocation. The actions of ET‐1 were shown to be mediated through the extracellular signal‐regulated kinases (ERKs) and protein kinase B (PKB) pathways, but signaling was demonstrated to be prevented by EGCG pretreatment.ConclusionsThese data suggest that EGCG mediates the acute and chronic effects of ET‐1 on 3T3‐L1 adipocyte glucose uptake via the respective alteration of Glut‐4 translocation and Glut‐1 protein levels and via the ERK and PKB pathways.