title: Activation of 5' adenosine monophosphate-activated protein kinase blocks cumulus cell expansion through inhibition of protein synthesis during in vitro maturation in Swine.
abstract: The serine/threonine kinase 5' adenosine monophosphate-activated protein kinase (AMPK), a heterotrimeric protein known as a metabolic switch, is involved in oocyte nuclear maturation in mice, cattle, and swine. The present study analyzed AMPK activation in cumulus cell expansion during in vitro maturation (IVM) of porcine cumulus-oocyte complexes (COC). 5-Aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) is a well-known activator of AMPK. It inhibited oocyte meiotic resumption in COC. Moreover, cumulus cell expansion did not occur in the presence of AICAR, demonstrating its marked impact on cumulus cells. Activation of AMPK was supported by AICAR-mediated phosphorylation of alpha AMPK subunits. Furthermore, the presence of AICAR increased glucose uptake, a classical response to activation of this metabolic switch in response to depleted cellular energy levels. Neither nuclear maturation nor cumulus expansion was reversed by glucosamine, an alternative substrate in hyaluronic acid synthesis, through the hexosamine biosynthetic pathway, which ruled out possible depletion of substrates. Both increased gap junction communication and phosphodiesterase activity in COC are dependent on protein synthesis during the initial hours of IVM; however, both were inhibited in the presence of AICAR, which supports the finding that activation of AMPK by AICAR mediated inhibition of protein synthesis. Moreover, this protein synthesis inhibition was equivalent to that of the well-known protein synthesis inhibitor cycloheximide, as observed on cumulus expansion and protein concentration. Finally, the phosphorylation level of selected kinases was investigated. The pattern of raptor phosphorylation is supportive of activation of AMPK-mediated inhibition of protein synthesis. In conclusion, AICAR-mediated AMPK activation in porcine COC inhibited cumulus cell expansion and protein synthesis. These results bring new considerations to the importance of this kinase in ovarian physiology and to the development of new oocyte culture medium.
authors.affiliation: Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec, Québec, Canada.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Santiquet
authors.affiliation: Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec, Québec, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Sasseville
authors.affiliation: Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec, Québec, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Laforest
authors.affiliation: Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec, Québec, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: Guillemette
authors.affiliation: Robinson Institute, Research Centre for Reproductive Health, School of Paediatrics and Reproductive Health, Medical School, University of Adelaide, Adelaide, Australia.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Gilchrist
authors.affiliation: Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Québec, Québec, Canada francois.richard@fsaa.ulaval.ca.
authors.forename: François J
authors.initials: FJ
authors.lastname: Richard
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D054885:Cumulus Cells / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D059471:In Vitro Oocyte Maturation Techniques / Q000662:veterinary*; D012265:Ribonucleotides / Q000494:pharmacology; D013552:Swine / Q000502:physiology*
chemical_list: D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide; D005947:Glucose
keywords: IVM; cumulus cells; in vitro maturation; kinases; oocyte maturation