Overexpression of Glucose Transporter 1 (GLUT1) Modulates Gonadotrope Function

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 134-163-GnRH & Gonadotroph Biology & Signaling
Bench to Bedside
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-154
Colleen Buggs-Saxton*, Omar Basha, Ahmad El-Yaman EL-Dandachli and Francina Gonzalez De Los Santos
Wayne State University School of Medicine, Detroit, MI
Introduction: Studies have shown that glucose availability is important for normal activity of the hypothalamus-pituitary-gonadal (H-P-G) axis.  Glucose transporters facilitate entry of glucose into cells, and we have previously shown that gonadotropin releasing hormone (GnRH) stimulates glucose transporter 1 (GLUT1) gene expression and glucose uptake in the gonadotrope cell.  In this study we investigated the effect of GLUT1 overexpression on gonadotrope function. 

Objective:To examine whether GLUT1 overexpression modulates gonadotrope function.

MethodsLßT2 gonadotrope cells were stably transfected with a CMV vector carrying the mouse Glut1 gene or CMV vector alone.  Stable clones of LßT2-CMV and LßT2-GLUT1 cells were selected using antibiotic resistance.  RNA was isolated from stable cells (basal condition without GnRH stimulation) and used for real-time PCR analysis to examine changes in gene expression (GLUT1, luteinizing hormone (LHß), follicle stimulating hormone (FSHß), GnRH receptor (GnRHr), and early growth response gene 1 (Egr-1).  Whole cell extracts were isolated from stable cells (basal condition without GnRH stimulation) and used in Western blot analysis with GLUT1 antibody.  Immunofluorescence analyses were performed to detect subcellular localization of GLUT1 and LH.  Glucose-uptake assays were also performed.

Results: Real-time PCR analysis of LßT2-GLUT1 cells showed a 7.6-fold increase in GLUT1 gene expression compared to LßT2-CMV cells (P< 0.05).  LßT2-GLUT1 cells also showed a 4.6-fold increase in expression of LHß mRNA, and a 22.1-fold increase in FSHß mRNA compared to LßT2-CMV cells (P < 0.05 ).  There were no changes in expression of GnRHr or Egr-1 genes in LßT2-Glut1 compared to LßT2-CMV.  Western blot analysis showed increased levels of GLUT1 protein in LßT2-GLUT1 compared to LßT2-CMV cells.  Immunofluorescence analysis showed that GLUT1 overexpression was associated with increased levels of LHß protein in LßT2-Glut1 cells compared to LßT2-CMV cells.  LßT2-GLUT1 cells showed increased glucose uptake compared to LßT2-CMV cells.

Conclusions:  Glut1 overexpression in LßT2 cells increases gonadotropin gene expression and protein synthesis in the absence of GnRH.  Our data suggest that GLUT1 may play a novel role in GnRH signaling which can modulate gonadotrope function and may provide new insights into the regulation of the H-P-G axis and puberty.

Nothing to Disclose: CB, OB, AEYE, FG

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Wayne State University School of Medicine Children's Hospital of Michigan