Proposed model of the neferine-induced increase in glucose uptake. Neferine promotes GLUT4 expression via the G protein-PLC-PKC and AMPK pathways, thereby enhancing both GLUT4 fusion with the plasma membrane and glucose uptake. Neferine also increases intracellular Ca2+ concentration through the G protein-PLC-IP3-IP3R pathway in L6 cells. Thus, neferine-induced GLUT4 fusion with the plasma membrane and glucose uptake are both Ca2+-dependent.