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Evidence for the Presence of Glucose Transporter 4 in the Endometrium and Its Regulation in Polycystic Ovary Syndrome Patients

Department of Medical and Surgical Sciences (R.M., N.X., L.Z., M.G., P.M., C.M., N.S., R.V.), Clinica Medica 3; Department of Oncological and Surgical Sciences (S.C., S.B.), Section of Pathology; and Department of Gynaecological and Human Reproduction Sciences (B.M.), University of Padova, 35128 Padova, Italy

Address all correspondence and requests for reprints to: Dr. Roberto Mioni, M.D., Ph.D., Dipartimento di Scienze Mediche e Chirurgiche, Clinica Medica 3, Università di Padova, Via Giustiniani 2, 35128 Padova, Italy. E-mail: robertomioni{at}libero.it.

Glucose transporter 4 (GLUT4) seems to be involved in the mechanism of insulin resistance in polycystic ovary syndrome (PCOS) patients (PCOSs) in both muscular and adipose tissue. The observation that insulin stimulates glucose oxidation in endometrial cells led us to investigate the presence of GLUT4 in this tissue and whether a defect of GLUT4 is present at the endometrial level in PCOSs. We also investigated whether body weight influences GLUT4 expression in this syndrome. GLUT4 mRNA content was examined by real-time quantitative RT-PCR and immunostaining reaction in the endometrial tissue of nine normal subjects, nine lean and eight obese hyperinsulinemic (h-INS), and eight lean and 10 obese normoinsulinemic (n-INS) PCOSs. GLUT4 mRNA and its positive immunostaining reaction were present in epithelial cell level in the endometrium of both normal and PCOS subjects. Significantly higher levels of GLUT4 were observed in normal and lean n-INS PCOSs in comparison with other groups. In both n-INS and h-INS obese PCOSs, GLUT4 was significantly lower than in lean subjects. However, obese n-INS and lean h-INS PCOSs showed a similar low GLUT4 expression, whereas obese h-INS PCOSs showed the lowest expression when compared with other groups. In conclusion, our data demonstrate that GLUT4 is present in the endometrium of normal and PCOS subjects and that hyperinsulinism and obesity seem to have a negative effect on endometrial GLUT4 expression in PCOS.

This work was supported by a grant from the Ministero Istruzione Universita Ricerca (to R.V.).

Abbreviations: AUC, Area under the curve; BMI, body mass index; CV, coefficient of variation; GLUT, glucose transporter; ISI, insulin sensitivity index; n-INS, normal insulin response; h-INS, hyperinsulinemic; OGTT, oral glucose tolerance test; PCOS, polycystic ovary syndrome; PCOSs, PCOS patients; r18S, ribosomal 18 subunit.