title: GLUT1 activity contributes to the impairment of PEDF secretion by the RPE.
abstract: In this study, we aimed to understand whether glucose transporter 1 (GLUT1) activity affects the secretion capacity of antiangiogenic factor pigment epithelium-derived factor (PEDF) by the RPE cells, thus explaining the reduction in PEDF levels observed in patients with diabetic retinopathy (DR).
  
  
  
  Analysis of GLUT1 expression, localization, and function was performed in vitro in RPE cells (D407) cultured with different glucose concentrations, corresponding to non-diabetic (5 mM of glucose) and diabetic (25 mM of glucose) conditions, further subjected to normoxia or hypoxia. The expression of PEDF was also evaluated in the secretome of the cells cultured in these conditions. Analysis of GLUT1 and PEDF expression was also performed in vivo in the RPE of Ins2(Akita) diabetic mice and age-matched wild-type (WT) controls.
  
  
  
  We observed an increase in GLUT1 under hypoxia in a glucose-dependent manner, which we found to be directly associated with the translocation and stabilization of GLUT1 in the cell membrane. This stabilization led to an increase in glucose uptake by RPE cells. This increase was followed by a decrease in PEDF expression in RPE cells cultured in conditions that simulated DR. Compared with non-diabetic WT mice, the RPE of Ins2(Akita) mice showed increased GLUT1 overexpression with a concomitant decrease in PEDF expression.
  
  
  
  Collectively, our data show that expression of GLUT1 is stimulated by hyperglycemia and low oxygen supply, and this overexpression was associated with increased activity of GLUT1 in the cell membrane that contributes to the impairment of the RPE secretory function of PEDF.
authors.affiliation: PhD Program in Biomedical Sciences, Department of Biomedical Sciences and Medicine, University of Algarve, Campus Gambelas, Faro, Portugal; CEDOC, NOVA Medical School | Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, Lisboa, Portugal.
authors.forename: Sofia M
authors.initials: SM
authors.lastname: Calado
authors.affiliation: CEDOC, NOVA Medical School | Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, Lisboa, Portugal; ProRegeM PhD Program, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, Lisboa, Portugal.
authors.forename: Liliana S
authors.initials: LS
authors.lastname: Alves
authors.affiliation: CEDOC, NOVA Medical School | Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, Lisboa, Portugal; Centre for Biomedical Research (CBMR), University of Algarve, Campus Gambelas, Faro, Portugal.
authors.forename: Sónia
authors.initials: S
authors.lastname: Simão
authors.affiliation: CEDOC, NOVA Medical School | Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, Lisboa, Portugal.
authors.forename: Gabriela A
authors.initials: GA
authors.lastname: Silva
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D003930:Diabetic Retinopathy / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D005947:Glucose / Q000494:pharmacology; D051272:Glucose Transporter Type 1 / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009414:Nerve Growth Factors / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism; D015843:Serpins / Q000378:metabolism*; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D005136:Eye Proteins; D005947:Glucose; D051272:Glucose Transporter Type 1; D009414:Nerve Growth Factors; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor; C495677:SLC2A1 protein, human; C495678:Slc2a1 protein, mouse