Improvement Of Glucosamine-induced Insulin Resistance In HepG2 Cells By Honokiol

Magnoliae officinalis Cortex(M.officinalis)is the dried bark of stem,root and branches of either Magnolia officinalis Rehder & E.H.Wilson or Magnolia officinalis var.biloba Rehder& E.H.Wilson,which can be applied since ancient times in the treatment of Qi stagnation according to Traditional Chinese Medicine(TCM).Liver-Qi stagnation syndrome is a frequent finding during the early period of type 2 diabetes(T2D).Honokiol,a natural biphenolic compound derived from M.officinalis,has protective effects against liver damage by attenuating hepatic lipid accumulation and oxidative injury,but its effects on insulin resistance accompanied by redox imbalance in human hepatocytes still remain unclear.The purpose of this study was to investigate the effects of honokiol on insulin resistance and oxidative stress after glucosamine treatment in hepatocytes,and whether AMPK activation is involved in the effects of honokiol.In this study,we obtained the following results:1.Glucose consumption and 2-NBDG uptake of HepG2 cells were significantly reduced by treating with 18 m M glucosamine in low glucose serum-free medium,indicating that insulin resistance in vitro model was successfully established.2.Molecular docking results revealed that honokiol could be binding into the same active site of AMPK agonist,suggesting that honokiol was an effective activator to AMPK.The phosphorylation of AMPK in HepG2 cells was significantly decreased after treating with glucosamine.Honokiol reversed glucosamine-induced inhibition of AMPK phosphorylation,and increased glucose consumption,promoted GLUT2 translocation to the plasma membrane and elevated 2-NBDG uptake in glucosamine-induced HepG2 cells,indicating that honokiol ameliorate insulin resistance.Pretreatment of with Compound C,an inhibitor of AMPK,these effects of honokiol on insulin resistance were largely abolished.These results suggested that honokiol improved glucosamine-induced insulin resistance by activating AMPK.3.After 18 m M glucosamine treatment,accumulation of ROS and impairment of mitochondrial membrane potential were observed in HepG2 cells.Honokiol reduced glucosamine-induced ROS accumulation and mitochondrial membrane potential loss in HepG2 cells,suggesting that honokiol can alleviate glucosamine-induced oxidative stress.Compound C pretreatment largely eliminated the alleviating effects of honokiol on oxidative stress.These results suggested that honokiol ameliorated glucosamine-induced oxidative stress by activating AMPK.Collectively,our results suggested that honokiol improved insulin resistance and alleviates oxidative stress by activating glucosamine-induced AMPK in HepG2 cells.This might be one of the mechanisms by which honokiol has beneficial effects on T2 D.Our findings provide novel into the mechanism of honokiol’s anti-diabetes effect.