title: Metformin decreases IGF1-induced cell proliferation and protein synthesis through AMP-activated protein kinase in cultured bovine granulosa cells.
abstract: Although its mechanism of action is still unclear, metformin is an anti-diabetic drug effective to restore cyclicity and spontaneous ovulation in women with polycystic ovary syndrome. It may also reduce the risk of cancer. We have recently shown that metformin treatment decreases steroidogenesis through AMP-activated kinase (AMPK) in granulosa cells of various species. Here, we investigated the effects and the molecular mechanisms of metformin in IGF1-induced proliferation and protein synthesis in cultured bovine granulosa cells. Treatment with metformin (10 mM) for 24 h reduced cell proliferation and the levels of cyclin D2 and E, and increased the associations cyclin D2/p21 and cyclin D2/p27 without affecting cell viability in response to IGF1 (10(-8) M). It also decreased IGF1-induced protein synthesis and phosphorylation of P70S6 kinase and ribosomal S6 protein. Interestingly, metformin treatment for 1 h decreased MAPK3/1 (ERK1/2) and P90RSK phosphorylation without affecting AKT phosphorylation in response to IGF1. Adenovirus-mediated expression of dominant-negative AMPK totally abolished the effects of metformin on cell proliferation and phosphorylation of P70S6K in response to IGF1. It also eliminated the inhibitory effects of metformin on MAPK3/1 and P90RSK phosphorylation. Taken together, our results strongly suggest that metformin reduces cell growth, protein synthesis, MAPK3/1, and P90RSK phosphorylation in response to IGF1 through an AMPK-dependent mechanism in cultured bovine granulosa cells.
authors.affiliation: Unité de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique (INRA), UMR85, F-37 380 Nouzilly, France Unité de Recherches Avicoles, INRA, URA83, F-37 380 Nouzilly, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Tosca
authors.forename: Christelle
authors.initials: C
authors.lastname: Ramé
authors.forename: Christine
authors.initials: C
authors.lastname: Chabrolle
authors.forename: Sophie
authors.initials: S
authors.lastname: Tesseraud
authors.forename: Joëlle
authors.initials: J
authors.lastname: Dupont
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D056742:Cyclin D2 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D005300:Fertility Agents, Female / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008687:Metformin / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
chemical_list: D056742:Cyclin D2; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005300:Fertility Agents, Female; D011994:Recombinant Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D007334:Insulin-Like Growth Factor I; D008687:Metformin; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D055372:AMP-Activated Protein Kinases