title: The effects of intravenous, glucose versus saline on ovarian follicles and their levels of some mediators of insulin signalling.
abstract: BACKGROUND
  A short-term increase in food intake and specifically dietary energy can stimulate folliculogenesis and increase ovulation rate in ewes. The mechanism appears to involve the insulin-glucose metabolic system and its interaction with FSH signalling pathways in the granulosa cells of ovarian follicles. This experiment was designed to investigate the interaction between these two systems in the granulosa cells of ovarian follicles.
  
  
  METHODS
  Thirty six Ile-de-France ewes were used in this controlled experiment to study the effects of intravenous glucose on folliculogenesis. Eighteen ewes were infused with glucose (10 mM/h for 72 h) from day 8 of the oestrous cycle, while the others (controls) received saline. Ovaries were collected when the infusions ended (luteal phase) or 30 h later and after a luteolytic dose of a PGF2α analogue (follicular phase). Follicles were dissected and granulosa cells and follicular fluid harvested. The blood concentrations of glucose, insulin, oestradiol and FSH were monitored over the experiment. The levels of Aromatase P450 and of the phosphorylated and non-phosphorylated forms of Akt, AMPK and ERK in granulosa cells and the concentration of oestradiol in follicular fluid, were determined.
  
  
  RESULTS
  Glucose increased the circulating concentration of glucose (P < 0.05) and insulin (P < 0.05). It also increased the total number of follicles >1.0 mm in diameter (P < 0.05) and small (P < 0.05) follicles (>1.0 to 2.0 mm in diameter) but not medium (>2.0 to 3.5 mm in diameter) or large (>3.5 mm in diameter) follicles. Glucose decreased circulating oestradiol (P < 0.05) but not that of FSH or progesterone. Glucose reduced aromatase P450 (P < 0.05) and decreased the phosphorylation of Akt (P < 0.05), ERK (P < 0.05) and AMPK (P < 0.05) in granulosa cells from oestrogenic follicles. The level of Aromatase P450 was greatest in large oestrogenic follicles and the phosphorylation of Akt (P < 0.05), ERK (P < 0.05) and AMPK (P < 0.05) was lower in small follicles compared to medium and large follicles.
  
  
  CONCLUSIONS
  These data suggest that the effect of glucose in small follicles is a direct action of glucose that increases the number of small follicles while the effect of glucose in oestrogenic follicles is an indirect insulin-mediated action.
authors.affiliation: L'Institut National de la Recherche Agronomique, Unité Mixte de Recherche 6175, Physiologie de la Reproduction et des Comportements, Nouzilly, 37380, France. rex.scaramuzzi@orange.fr.|Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, North Mimms, Hertfordshire, AL9 7TA, UK. rex.scaramuzzi@orange.fr.
authors.forename: Rex John
authors.initials: RJ
authors.lastname: Scaramuzzi
authors.affiliation: L'Institut National de la Recherche Agronomique, Unité Mixte de Recherche 6175, Physiologie de la Reproduction et des Comportements, Nouzilly, 37380, France. zouaidi_nesrine@yahoo.fr.
authors.forename: Nesrine
authors.initials: N
authors.lastname: Zouaïdi
authors.affiliation: L'Institut National de la Recherche Agronomique, Unité Mixte de Recherche 6175, Physiologie de la Reproduction et des Comportements, Nouzilly, 37380, France. jean-baptiste.menassol@clermont.inra.fr.|L'Institut National de la Recherche Agronomique, UR 1213 URH Unité de Recherches sur les Herbivores, Centre de recherche de Clermont-Ferrand-Theix, Clermont-Ferrand, France. jean-baptiste.menassol@clermont.inra.fr.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Menassol
authors.affiliation: L'Institut National de la Recherche Agronomique, Unité Mixte de Recherche 6175, Physiologie de la Reproduction et des Comportements, Nouzilly, 37380, France. joelle.dupont@tours.inra.fr.
authors.forename: Joëlle
authors.initials: J
authors.lastname: Dupont
mesh_terms: D061605:Administration, Intravenous; D000818:Animals; D001141:Aromatase / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D015571:Follicular Fluid / Q000187:drug effects / Q000378:metabolism; D005498:Follicular Phase / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D006080:Ovarian Follicle / Q000187:drug effects* / Q000378:metabolism; D010060:Ovulation / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D012756:Sheep; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D004958:Estradiol; D005640:Follicle Stimulating Hormone; D001141:Aromatase; D005947:Glucose