5′-AMP-activated protein kinase plays an essential role in geniposide-regulated glucose-stimulated insulin secretion in rat pancreatic INS-1 β cells

Our previous work showed that geniposide affected glucose-stimulated insulin secretion (GSIS) via regulating glucose uptake and metabolism in pancreatic beta cells; however, the molecular mechanisms remain largely unknown. Substantial evidence suggests that activation of 5'-AMP-activated protein kinase (AMPK) plays a central role in GSIS. Here, we aim to determine the role of AMPK on geniposide-regulated GSIS in rat pancreatic INS-1 cells. The results demonstrated that 6-[4-(2-piperidin-1-yletoxy)-phenyl]-3-pyridin-4-yl-pyrazolo[1,5-alpha] pyrimidine (Compound C; an AMPK inhibitor) significantly attenuated the effects of geniposide on glucose uptake, energy metabolism, and insulin secretion in INS-1 cells. We also observed that geniposide induced phosphorylation of acetyl-CoA carboxylase (ACC), a marker of AMPK activity, in a time-dependent manner in INS-1 cells; however, in the presence of Compound C, the influence of geniposide on ACC phosphorylation was obviously inhibited. Furthermore, the knockdown of AMPK protein with AMPK siRNA treatment decreased the effects of geniposide on glucose uptake, adenosine triphosphate production, and GSIS. All these data indicate that AMPK plays an essential role in geniposide-regulated GSIS in pancreatic beta cells.

我们先前的研究表明，栀子苷通过调节胰腺β细胞的葡萄糖摄取和代谢来影响葡萄糖刺激的胰岛素分泌（GSIS）；然而，其分子机制在很大程度上仍然未知。大量证据表明，5'-腺苷酸活化蛋白激酶（AMPK）的激活在GSIS中起核心作用。在此，我们旨在确定AMPK在大鼠胰腺INS - 1细胞中对栀子苷调节的GSIS的作用。结果表明，6 - [4 - (2 - 哌啶 - 1 - 基乙氧基) - 苯基] - 3 - 吡啶 - 4 - 基 - 吡唑并[1,5 - α]嘧啶（化合物C；一种AMPK抑制剂）显著减弱了栀子苷对INS - 1细胞葡萄糖摄取、能量代谢和胰岛素分泌的影响。我们还观察到栀子苷在INS - 1细胞中以时间依赖性方式诱导乙酰辅酶A羧化酶（ACC）的磷酸化，ACC是AMPK活性的标志物；然而，在化合物C存在的情况下，栀子苷对ACC磷酸化的影响明显受到抑制。此外，用AMPK小干扰RNA处理降低AMPK蛋白水平减弱了栀子苷对葡萄糖摄取、三磷酸腺苷产生和GSIS的影响。所有这些数据表明，AMPK在胰腺β细胞中栀子苷调节的GSIS中起关键作用。