The Machnism For Several Bitter Tastants Promoting GLUT4 Translocation

Bitter tastants are usually considered to be an efficient medicine for the treatment of many diseases.As the saying goes,good medicine always tastes bitter,which is certification of this view.Bitter tastants have refreshing,antifebrile,cooling and stomachic functions.It concludes quassin,alkaloids,amino acids,vitamins and minerals,etc.,witch can help promote digestion,relieve inflammation and enhance appetite,and also to exclude toxins,vent hearts hot.Chloroquine,as a representative of the bitter tastants,was originally used to treat malaria,which taste very bitter.With the deepening of scientific research,its roles in many other effects are constantly being discovered.As early as 1991,scientists have demonstrated that chloroquine can enhance the role of insulin to promote glucose uptake,but the specific mechanism is still unclear.In traditional Chinese medicine,bitter tastants are also known as bitter and cold Chinese medicines,which have been long used for the treatment of DM since thousands of years ago in China.However,many of the principles of traditional Chinese medicine and the role of antidiabetic mechanism remain unclear up to now.In this article,to find potential antidiabetic drugs and further explore its possible mechanism and principle,we aim at screening different bitter tastants included western medicine and traditional Chinese medicine.In this paper,we first experiment for chloroquine,the representative of bitter tastants in western medicine.Here,GLUT4 translocation and intracellular Ca2+ in L6 cells stably overexpressing IRAP-mOrange were observed by confocal microscope.GLUT4 fusion with the plasma membrane(PM)was traced using HA-GLUT4-GFP.Glucose uptake was measured by cell-based glucose uptake assay kit.GLUT4 mRNA and protein were detected by RT-PCR and western blotting,respectively.The results found that chloroquine induced a series of significant increases in GLUT4 translocation to and fusion with the PM,glucose uptake,and intracellular Ca2+ in L6 muscle cells.Gallein(Gβγ inhibitor)and U73122(PLC inhibitor)inhibited chloroquine-induced increases in GLUT4 translocation and intracellular Ca2+.However,2-APB(IP3R inhibitor)only blocked intracellular Ca2+ increase.These results indicate that chloroquine,via the Gβγ-PLC-IP3-IP3 R pathway,induces Ca2+ elevation,which was not associated with the chloroquine-evoked GLUT4 translocation increase.However,GLUT4 fusion and glucose uptake were significantly inhibited by BAPTA-AM suggesting that Ca2+ enhances GLUT4 fusion,resulting in glucose uptake increased.The mechanisms ultimately stimulated-glucose uptake increasing is not only in control and also in insulin-resistant L6 cells.These findings suggest the potential of chloroquine as a bitter drug for improving insulin tolerance in DM patients.Secondly,we also discussed two different traditional bitter and cold Chinese medicine-Sophora flavescens EtOAc extract(SF-EtOAc)and Berberis julianae Schneid.extract(BJSME),whose relationship and specific machanism with GLUT4 translocation.We observed the change of the IRAP fluorescence intensity in L6 cells by confocal,which suggest that SF-EtOAc and BJSME can obviously promote the GLUT4 tranfficking respectively.Besides,the Compound C(AMPK inhibitor)could inhibit GLUT4 translocation,both under the stimulation of SF-EtOAc and BJSME.These indicate that SF-EtOAc-and BJSME-induced GLUT4 tranfficking are mainly regulated by AMPK activity,the results also were proved in muscle tissues of T2 DM modle mice.Thus,SF-EtOAc and BJSME may be potential therapeutic agents for patients with T2 DM.Taken together,we aim at exploring the potential effects of bitter tastants,looking for drugs to promote GLUT4 translocation to PM in insulin resistance and T2 DM patients.In results,it is possible to obtain antidiabetic drugs that can relieve the pain of insulin tolerance on diabetes patients.