title: Characterization of the effects of metformin on porcine oocyte meiosis and on AMP-activated protein kinase activation in oocytes and cumulus cells.
abstract: The adenosine monophosphate-activated protein kinase (AMPK) activators 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR) and metformin (MET) inhibit resumption of meiosis in porcine cumulus-enclosed oocytes. The objective of this study was to characterize the inhibitory effect of MET on porcine oocyte meiosis by: (1) determining the effects of an AMPK inhibitor and of inhibitors of signalling pathways involved in MET-induced AMPK activation in other cell types on MET-mediated meiotic arrest in porcine cumulus-enclosed oocytes; (2) determining whether MET and AICAR treatments lead to increased activation of porcine oocyte and/or cumulus cell AMPK as measured by phosphorylation of its substrate acetyl-CoA carboxylase; and (3) determining the effects of inhibition of the AMPK kinase, Ca2+/calmodulin-dependent protein kinase kinase (CaMKK), and Ca2+ chelation on oocyte meiotic maturation and AMPK activation in porcine oocytes and cumulus cells. The AMPK inhibitor compound C (CC; 1 μM) did not reverse the inhibitory effect of AICAR (1 mM) and MET (2 mM) on porcine oocyte meiosis. Additionally, CC had a significant inhibitory effect on its own. eNOS, c-Src and PI-3 kinase pathway inhibitors did not reverse the effect of metformin on porcine oocyte meiosis. The level of acetyl-CoA carboxylase (ACC) phosphorylation in oocytes and cumulus cells did not change in response to culture in the presence of MET, AICAR, CC, the CaMKK inhibitor STO-609 or the Ca2+ chelator BAPTA-AM for 3 h, but STO-609 increased the percentage of porcine cumulus-enclosed oocytes (CEO) that remained at the germinal vesicle (GV) stage after 24 h of culture. These results indicate that the inhibitory effect of MET and AICAR on porcine oocyte meiosis was probably not mediated through activation of AMPK.
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge Research Centre 5403 1st Avenue South, Lethbridge, Alberta T1J 4B1, Canada.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Bilodeau-Goeseels
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge Research Centre, 5403 1st Avenue South, Lethbridge, Alberta T1J 4B1, Canada.
authors.forename: Nora
authors.initials: N
authors.lastname: Magyara
authors.affiliation: VetAgro Sup Campus Agronomique de Clermont-Ferrand, 89 Avenue de l'Europe, 63 370 Lempdes, France.
authors.forename: Coralie
authors.initials: C
authors.lastname: Collignon
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D054885:Cumulus Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008540:Meiosis / Q000187:drug effects* / Q000502:physiology; D008687:Metformin / Q000494:pharmacology*; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D013552:Swine
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin; D055372:AMP-Activated Protein Kinases