Characterization of GAB1 expression over the menstrual cycle in women with and without polycystic ovarian syndrome provides a new insight into its pathophysiology

J Clin Endocrinol Metab. 2014 Nov;99(11):E2162-8. doi: 10.1210/jc.2014-2128. Epub 2014 Aug 21.

Abstract

Context: In a previous microarray analysis, GRB2-associated binding protein 1 (GAB1), a docking protein closely related to the insulin receptor substrate, was down-regulated in endometrium of women with polycystic ovary syndrome (PCOS).

Objective: The objective of the study was to characterize the cyclic expression of endometrial GAB1 in vivo in normal women and those with PCOS as well as investigate the possible mechanisms of endometrial regulation of GAB1 expression and action in vitro.

Design: This was an experimental and case-control study.

Setting: The study was conducted at a tertiary university hospital.

Patients: Normal proven fertile women (controls; n = 31) and women with PCOS (cases; n = 26) participated in the study.

Interventions: INTERVENTIONS included timed endometrial biopsies at different phases of the menstrual cycle. Ishikawa cells were cultured with β-estradiol (E2), medroxyprogesterone acetate, and E2 + medroxyprogesterone acetate. Transfection of small interfering RNA for GAB1 in Ishikawa cells incubated with or without insulin.

Main outcome measures: GAB1 mRNA expression in Ishikawa cells and in endometrium of cases and controls was measured. Protein expression of phosphorylated MAPK by Western blot was also measured. Immunohistochemical localization and expression of phosphorylated GAB1 in endometrium was also measured, using a digital histological score.

Results: In endometrial tissue, GAB1 mRNA was reduced in the proliferative phase of PCOS women, compared with controls (P = .003; ANOVA). When all the phases of the menstrual cycle were grouped, GAB1 protein expression was reduced in endometrium of PCOS women (P < .0001; Student t test). E2 increases GAB1 mRNA expression in Ishikawa cells (P = .001; ANOVA). Phosphorylated MAPK is reduced in cells transfected with small interfering RNA for GAB1 (P = .008; ANOVA) and incubated with insulin.

Conclusions: GAB1 mRNA expression is positively modulated by E2. Endometrial GAB1 protein and mRNA expression are reduced in women with PCOS, suggesting that the endometrium of PCOS women have a defect in insulin signaling due to GAB1 down-regulation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adult
  • Case-Control Studies
  • Cell Line, Tumor
  • Down-Regulation
  • Endometrium / cytology
  • Endometrium / drug effects
  • Endometrium / metabolism*
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Estradiol / pharmacology
  • Female
  • Humans
  • Medroxyprogesterone Acetate / pharmacology
  • Menstrual Cycle / genetics
  • Menstrual Cycle / metabolism*
  • Phosphorylation / drug effects
  • Polycystic Ovary Syndrome / genetics
  • Polycystic Ovary Syndrome / metabolism*
  • Signal Transduction / drug effects
  • Young Adult

Substances

  • Adaptor Proteins, Signal Transducing
  • GAB1 protein, human
  • Estradiol
  • Medroxyprogesterone Acetate