Hawley Simon A, Gadalla Anne E, Olsen Grith Skytte, Hardie D Grahame
Division of Molecular Physiology, School of Life Sciences and Wellcome Trust Biocentre, Dundee University, Dundee, Scotland, UK.
Diabetes. 2002 Aug;51(8):2420-5. doi: 10.2337/diabetes.51.8.2420.
Metformin, a drug widely used to treat type 2 diabetes, was recently shown to activate the AMP-activated protein kinase (AMPK) in intact cells and in vivo. In this study we addressed the mechanism for this effect. In intact cells, metformin stimulated phosphorylation of the key regulatory site (Thr-172) on the catalytic (alpha) subunit of AMPK. It did not affect phosphorylation of this site by either of two upstream kinases in cell-free assays, although we were able to detect an increase in upstream kinase activity in extracts of metformin-treated cells. Metformin has been reported to be an inhibitor of complex 1 of the respiratory chain, but we present evidence that activation of AMPK in two different cell types is not a consequence of depletion of cellular energy charge via this mechanism. Whereas we have not established the definitive mechanism by which metformin activates AMPK, our results show that the mechanism is different from that of the existing AMPK-activating agent, 5-aminoimidazole-4-carboxamide (AICA) riboside. Metformin therefore represents a useful new tool to study the consequences of AMPK activation in intact cells and in vivo. Our results also show that AMPK can be activated by mechanisms other than changes in the cellular AMP-to-ATP ratio.
二甲双胍是一种广泛用于治疗2型糖尿病的药物，最近的研究表明，它在完整细胞和体内均可激活AMP激活的蛋白激酶（AMPK）。在本研究中，我们探讨了这种作用的机制。在完整细胞中，二甲双胍可刺激AMPK催化（α）亚基关键调节位点（Thr-172）的磷酸化。在无细胞实验中，它对两种上游激酶催化该位点的磷酸化均无影响，尽管我们能够检测到二甲双胍处理的细胞提取物中上游激酶活性有所增加。据报道，二甲双胍是呼吸链复合物I的抑制剂，但我们提供的证据表明，在两种不同细胞类型中AMPK的激活并非通过该机制导致细胞能量电荷耗竭的结果。虽然我们尚未确定二甲双胍激活AMPK的确切机制，但我们的结果表明，该机制不同于现有的AMPK激活剂5-氨基咪唑-4-甲酰胺（AICA）核苷。因此，二甲双胍是研究完整细胞和体内AMPK激活后果的一种有用的新工具。我们的结果还表明，AMPK可通过细胞内AMP与ATP比值变化以外的机制被激活。
