AMP-activated protein kinase (AMPK), which is a pivotal guardian of whole-body energy metabolism, has become an attractive therapeutic target for metabolic syndrome. Previously, using a homogeneous scintillation proximity assay, we identified the small-molecule AMPK activator C24 from an optimization based on the original allosteric activator PT1. In this paper, the AMPK activation mechanism of C24 and its potential beneficial effects on glucose and lipid metabolism on db/db mice were investigated. C24 allosterically stimulated inactive AMPK α subunit truncations and activated AMPK heterotrimers by antagonizing autoinhibition. In primary hepatocytes, C24 increased the phosphorylation of AMPK downstream target acetyl-CoA carboxylase dose-dependently without changing intracellular AMP/ATP ratio, indicating its allosteric activation in cells. Through activating AMPK, C24 decreased glucose output by down-regulating mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) in primary hepatocytes. C24 also decreased the triglyceride and cholesterol contents in HepG2 cells. Due to its improved bioavailability, chronic oral treatment with multiple doses of C24 significantly reduced blood glucose and lipid levels in plasma, and improved the glucose tolerance of diabetic db/db mice. The hepatic transcriptional levels of PEPCK and G6Pase were reduced. These results demonstrate that this orally effective activator of AMPK represents a novel approach to the treatment of metabolic syndrome.
Keywords: 5-aminoimidazole-4-carboxamide ribonucleoside; ACC; AICAR; AID; AMP-activated protein kinase; AMPK; Activator; Allosteric; CBS; CCCP; CNTF; CaMKKα/β; G6Pase; GBD; GSK3β; IKKβ; IκB kinase β; KD; MAP/microtubule affinity-regulating kinase 2; MARK2; MELK; Maternal Embryonic Leucine zipper Kinase; Metabolic syndrome; Orally effective; PEPCK; RER; S. pombe; SPA; Schizosaccharomyces pombe; Small-molecule; TAK1; acetyl-CoA carboxylase; autoinhibitory domain; calmodulin-dependent protein kinase kinase α/β; carbonyl cyanide m-chlorophenylhydrazone; ciliary neurotrophic factor; cystathionine beta synthase; glucose-6-phosphatase; glycogen synthase kinase 3β; glycogen-binding domain; intraperitoneal glucose tolerance test; ipGTT; kinase domain; phosphoenolpyruvate carboxykinase; respiratory exchange ratio; scintillation proximity assay; transforming growth factor-β-activated kinase1.
© 2013.