title: Metformin inhibits hepatic gluconeogenesis in mice independently of the LKB1/AMPK pathway via a decrease in hepatic energy state.
abstract: Metformin is widely used to treat hyperglycemia in individuals with type 2 diabetes. Recently the LKB1/AMP-activated protein kinase (LKB1/AMPK) pathway was proposed to mediate the action of metformin on hepatic gluconeogenesis. However, the molecular mechanism by which this pathway operates had remained elusive. Surprisingly, here we have found that in mice lacking AMPK in the liver, blood glucose levels were comparable to those in wild-type mice, and the hypoglycemic effect of metformin was maintained. Hepatocytes lacking AMPK displayed normal glucose production and gluconeogenic gene expression compared with wild-type hepatocytes. In contrast, gluconeogenesis was upregulated in LKB1-deficient hepatocytes. Metformin decreased expression of the gene encoding the catalytic subunit of glucose-6-phosphatase (G6Pase), while cytosolic phosphoenolpyruvate carboxykinase (Pepck) gene expression was unaffected in wild-type, AMPK-deficient, and LKB1-deficient hepatocytes. Surprisingly, metformin-induced inhibition of glucose production was amplified in both AMPK- and LKB1-deficient compared with wild-type hepatocytes. This inhibition correlated in a dose-dependent manner with a reduction in intracellular ATP content, which is crucial for glucose production. Moreover, metformin-induced inhibition of glucose production was preserved under forced expression of gluconeogenic genes through PPARgamma coactivator 1alpha (PGC-1alpha) overexpression, indicating that metformin suppresses gluconeogenesis via a transcription-independent process. In conclusion, we demonstrate that metformin inhibits hepatic gluconeogenesis in an LKB1- and AMPK-independent manner via a decrease in hepatic energy state.
authors.affiliation: Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France. marc.foretz@inserm.fr
authors.forename: Marc
authors.initials: M
authors.lastname: Foretz
authors.forename: Sophie
authors.initials: S
authors.lastname: Hébrard
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Leclerc
authors.forename: Elham
authors.initials: E
authors.lastname: Zarrinpashneh
authors.forename: Maud
authors.initials: M
authors.lastname: Soty
authors.forename: Gilles
authors.initials: G
authors.lastname: Mithieux
authors.forename: Kei
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Andreelli
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
mesh_terms: D055372:AMP-Activated Protein Kinases; D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism; D005943:Gluconeogenesis / Q000187:drug effects* / Q000235:genetics; D005947:Glucose / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D005952:Glucose-6-Phosphatase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism; D006943:Hyperglycemia / Q000235:genetics / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000378:metabolism / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008687:Metformin / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D005952:Glucose-6-Phosphatase; D019764:Phosphoenolpyruvate Carboxykinase (ATP); D005947:Glucose