Lack of cyclical fluctuations of endometrial GLUT4 expression in women with polycystic ovary syndrome: Evidence for direct regulation of GLUT4 by steroid hormones

Abstract

BackgroundDetermination of the role of steroid hormones in expression and regulation of endometrial glucose transport 4 (GLUT4) in humans is important for understanding endometrial disorders such as polycystic ovary syndrome (PCOS), a common hormone-imbalance disease.MethodsEndometrial biopsy samples were collected from non-PCOS patients with regular menstrual cycles or with hyperplasia and from PCOS patients with or without hyperplasia. In addition, endometrial tissues from postmenopausal women were incubated with human chorionic gonadotropin (hCG, 10 IU/ml), 17β-estradiol (E2, 10 nM), progesterone (P4, 100 nM), or a combination of E2 and P4 for 24 h. The expression of GLUT4 was measured at the mRNA level using quantitative real-time polymerase chain reaction (qRT-PCR) and at the protein level using Western blot analysis and immunohistochemistry.ResultsA cyclical change in GLUT4 expression pattern was observed in non-PCOS patients, and a high level of GLUT4 expression was seen in the proliferative phase compared to the secretory phase. Low levels of GLUT4 expression were found in PCOS patients compared to menstrual cycle phase-matched non-PCOS patients, and there was no significant change in GLUT4 expression in PCOS patients during the menstrual cycle. GLUT4 was localized in both epithelial and stromal cells, with notable changes in epithelial cells. We postulate that decreased GLUT4 expression might be regulated by steroid hormones. In support of this, we showed that in cultured endometrial tissues hCG and E2 alone had no effect on GLUT4 expression. However, P4 alone and P4 in combination with E2 decreased GLUT4 expression. Compared with non-PCOS controls, PCOS patients with endometrial hyperplasia exhibited decreased GLUT4 expression in particular in the epithelial cells.ConclusionWe conclude that P4 can induce changes in endometrial GLUT4 expression during the menstrual cycle and that abnormal hormonal conditions such as PCOS disrupt normal patterns of GLUT4 expression in endometrial cells.

Molecular characterization of insulin resistance and glycolytic metabolism in the rat uterus

“…These findings are in agreement with the conclusion that inadequate expression of different Glut isoforms in the uterus is associated with impaired cellular function 35 . Among the 12 Glut isoforms, decreased expression of endometrial Glut4, a major insulin-responsive glucose transporter, in PCOS patients 41 50 51 is confirmed in the insulin+hCG-treated rats. Furthermore, the protein profile of uterine tissues shows that the expression pattern of HK II, PKM1/2, PFKFB3, PFKL, enolase 2, and LDHA is different in the rat uterus between insulin and hCG treatment.…”

Differential Expression Patterns of Glycolytic Enzymes and Mitochondria-Dependent Apoptosis in PCOS Patients with Endometrial Hyperplasia, an Early Hallmark of Endometrial Cancer, In Vivo and the Impact of Metformin In Vitro

“…The culture conditions and dose and time for metformin treatment were as described previously 41, 42.…”

Regulation of Androgen Receptor Expression Alters AMPK Phosphorylation in the Endometrium: In Vivo and In Vitro Studies in Women with Polycystic Ovary Syndrome

“…All endometrial tissues were obtained by endometrial curettage of the bisected uteri obtained during hysterectomy for benign gynecological indications. Each endometrial sample was diagnosed and staged by routine pathology analysis based on standard histological criteria 38 , and the patient's last reported menstrual period was recorded at the time of collection 39 . Immunohistochemical staining of cysteine-rich 61 (Cyr61) with a confirmed histological diagnosis of simple or complex endometrial hyperplasia without cytological atypia was performed (Fig.…”

“…Tissue culture was essentially carried out as described previously 21 , 39 . Briefly, endometrial tissues from each woman in the proliferative phase of a normal menstrual cycle were treated with DHT (100 nM) and were incubated in a humidified incubator (37°C, 95% O 2 , 5% CO 2 ) for 24 h. On the second day, the tissues were further treated with DHT (100 nM) or DHT (100 nM) plus flutamide (10 μM) and were cultured for an additional 24 h. The selected doses of DHT and flutamide were according to previous studies 41 , 42 .…”

“…Endometrial and uterine tissues were extracted according to the previous studies 21 , 39 . A detailed explanation of the Western blot analysis and membrane stripping protocol has been published elsewhere 45 .…”