Regulation of insulin signaling and glucose transporters in the endometria of patients with polycystic ovary syndrome

Abstract

Objective: Subfertility associated with polycystic ovarian syndrome (PCOS) mainly originates from oligo/anovulation; however, factors related to blastocyst implantation and maintenance of pregnancy may also contribute. Although roles for insulin resistance and androgen excess have been suggested in the pathogenesis of PCOS-associated implantation failure, a comprehensive investigation of the consequences of PCOS on endometrial homeostasis and pathophysiology has not been performed. In this study, I investigated whether insulin sensitivity and glucose metabolism in the endometria of patients with PCOS are intrinsically altered. I also examined whether hyperandrogenic milieu affect glucose metabolism and the global gene expression patterns in cultured human endometrial stromal cells (hESCs), and studied the influence of hyperandrogenic conditions on facilitated glucose transporters (GLUTs) expression during in vitro decidualization of hESCs. Design: Experimental study involved the use of human endometrial tissues and a human endometrial cell line. Materials and Methods: Seven healthy women with regular menstrual cycles and 16 patients with PCOS were recruited for this study. Endometrial samples were obtained from the corpus of the uteri under sterile conditions. Control endometria were biopsied in the early proliferative phase, due to morphological and physiological similarities to those of patients with PCOS. Reverse transcription polymerase chain reaction (RT-PCR), real-time RT-PCR, and western blot analysis were performed to examine the levels of proteins involved in insulin signaling and glucose metabolism. To mimic hyperandrogenism and hyperinsulinemia in patients with PCOS in vitro, hESCs were treated with 1, 10, or 100 μM dihydrotestosterone (DHT) for 3 to 9 days and 10 nM insulin for 8 hours, respectively. In vitro decidualization was induced in hESCs by culture with 0.5 mM cAMP and 1 μM medroxyprogesterone 17-acetate for 1 to 9 days. Messenger RNA (mRNA) microarray experiments were performed with hESCs treated with 10 μM DHT, and data were analyzed using Gene Set Enrichment Analysis (GSEA). Results: In the endometria of patients with PCOS, GLUT1, GLUT12, insulin receptor (IR), and insulin receptor substrate (IRS) levels were significantly increased. However, no differences in expression were observed between the endometria of obese and lean patients with PCOS. Notably, GLUT4 mRNA was not detected in the endometria of patients with PCOS nor control subjects. Levels of phosphorylated IRS1 (p-IRS1) and phosphorylated Akt (p-Akt) were up-regulated in the lysates of both insulin- and androgen-treated hESCs. In addition, DHT treatment up-regulated the levels of GLUT1 and GLUT12 in cultured hESCs, suggesting that hyperandrogenic conditions affect glucose transport and/or metabolism. This notion was supported by mRNA microarray experiments, which further demonstrated that glucose transport and/or metabolism was dysregulated in hESCs by DHT treatment. During in vitro decidualization, the expression levels of GLUT1, 8, and 12 gradually increased. Of note, protein and mRNA levels of GLUT1 and 12 were decreased when decidualizing hESCs were treated with DHT, although these changes were not statistically significant. Conclusion: Hyperandrogenic milieu up-regulated the adaptor protein of insulin signaling as well as GLUTs in the endometria of patients with PCOS. Messenger RNA microarray experiments revealed androgen-induced dysregulation of glucose transport and/or metabolism in human endometrium. During decidualization, hyperandrogenic conditions down-regulated the expression of GLUTs, possibly causing impaired uterine receptivity.