This study investigated whether (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone (HM-chromanone) could counteract the high glucose level-induced blockade of insulin signaling in human HepG2 cells. Cells were pre-incubated with glucose (5.5 or 33 mM) and then incubated with a medium containing various concentrations of HM-chromanone. Assays for glucose uptake, glycogen synthesis, and glucose production were performed. Western blotting helped elucidate the underlying molecular mechanisms. High glucose concentration (33 mM) significantly increased p-IRS-1ser307 levels and decreased p-Akt levels. However, HM-chromanone significantly decreased p-IRS-1ser307 levels while increasing p-IRS-1tyr612 and Akt levels, which restored insulin signaling disturbed by high glucose concentration. HM-chromanone significantly increased p-AMPK levels, which were reduced by high glucose in HepG2 cells. Knockdown of AMPK using siRNA increased p-IRS-1ser307 and decreased p-Akt levels, even after treatment with HM-chromanone in high glucose concentration-treated cells. HM-chromanone stimulated glycogen synthesis by increasing p-GSK3βser9 and decreasing p-GSser641 levels in HepG2 cells under high glucose concentration; this effect was blocked by AMPK siRNA. HM-chromanone significantly decreased PEPCK, G6Pase, and hepatic glucose production, which were also blocked by AMPK siRNA. These results suggest that HM-chromanone could reverse insulin signaling blockade (induced by high glucose levels) through the activation of AMPK and stimulation of glucose uptake and glycogen synthesis in HepG2 cells.
Keywords: AMPK; Glucose uptake; HepG2; IRS-1; Insulin signaling.
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