title: Possible role of 5'AMP-activated protein kinase in the metformin-mediated arrest of bovine oocytes at the germinal vesicle stage during in vitro maturation.
abstract: The 5'AMP-activated protein kinase (AMPK) activation is involved in the meiotic maturation of oocytes in the ovaries of mice and pigs. However, its effects on the oocyte appear to be species-specific. We investigated the patterns of AMPK and mitogen-activated protein kinases (MAPK3/1) phosphorylation during bovine in vitro maturation (IVM) and the effects of metformin, an AMPK activator, on oocyte maturation in cumulus-oocyte complexes (COCs) and denuded bovine oocytes (DOs). In bovine COCs, PRKAA Thr172 phosphorylation decreased, whereas MAPK3/1 phosphorylation increased in both oocytes and cumulus cells during IVM. Metformin (5 and 10 mM) arrested oocytes at the GV stage in COCs but not in DOs. In COCs, this arrest was associated with the inhibition of cumulus cell expansion, an increase in PRKAA Thr172 phosphorylation, and a decrease in MAPK3/1 phosphorylation in both oocytes and cumulus cells. However, the addition of compound C (10 muM), an inhibitor of AMPK, accelerated the initiation of the GV breakdown (GVBD) process without any alteration of MAPK3/1 phosphorylation in oocytes from bovine COCs. Metformin decreased AURKA and CCNB1 protein levels in oocytes. Moreover, after 1 h of IVM, metformin decreased RPS6 phosphorylation and increased EEF2 phosphorylation, suggesting that protein synthesis rates were lower in oocytes from metformin-treated COCs. Most oocytes were arrested after the GVBD stage following the treatment of COCs with the MEK inhibitor, U0126 (100 micromoles). Thus, in bovine COCs, metformin blocks meiotic progression at the GV stage, activates PRKAA, and inhibits MAPK3/1 phosphorylation in both the oocytes and cumulus cells during IVM. Moreover, cumulus cells were essential for the effects of metformin on bovine oocyte maturation, whereas MAPK3/1 phosphorylation was not.
authors.affiliation: Unité de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique, 37380 Nouzilly, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Tosca
authors.forename: Svetlana
authors.initials: S
authors.lastname: Uzbekova
authors.forename: Christine
authors.initials: C
authors.lastname: Chabrolle
authors.forename: Joëlle
authors.initials: J
authors.lastname: Dupont
mesh_terms: D055372:AMP-Activated Protein Kinases; D000818:Animals; D015153:Blotting, Western / Q000662:veterinary; D002070:Butadienes / Q000494:pharmacology; D002417:Cattle; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D066298:In Vitro Techniques; D008687:Metformin / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D010766:Phosphorylation; D011374:Progesterone / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D009570:Nitriles; D011720:Pyrazoles; D011743:Pyrimidines; C113580:U 0126; C516138:dorsomorphin; D011374:Progesterone; D008687:Metformin; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D055372:AMP-Activated Protein Kinases