title: Insulin stimulated-glucose transporter Glut 4 is expressed in the retina.
abstract: The vertebrate retina is a very metabolically active tissue whose energy demands are normally met through the uptake of glucose and oxygen. Glucose metabolism in this tissue relies upon adequate glucose delivery from the systemic circulation. Therefore, glucose transport depends on the expression of glucose transporters. Here, we show retinal expression of the Glut 4 glucose transporter in frog and rat retinas. Immunohistochemistry and in situ hybridization studies showed Glut 4 expression in the three nuclear layers of the retina: the photoreceptor, inner nuclear and ganglionar cell layers. In the rat retina immunoprecipitation and Western blot analysis revealed a protein with an apparent molecular mass of 45 kDa. ¹⁴C-glucose accumulation by isolated rat retinas was significantly enhanced by physiological concentrations of insulin, an effect blocked by inhibitors of phosphatidyl-inositol 3-kinase (PI3K), a key enzyme in the insulin-signaling pathway in other tissues. Also, we observed an increase in ³H-cytochalasin binding sites in the presence of insulin, suggesting an increase in transporter recruitment at the cell surface. Besides, insulin induced phosphorylation of Akt, an effect also blocked by PI3K inhibition. Expression of Glut 4 was not modified in retinas of a type 1 diabetic rat model. To our knowledge, our results provide the first evidence of Glut4 expression in the retina, suggesting it as an insulin- responsive tissue.
authors.affiliation: División Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, Distrito Federal, México.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Sánchez-Chávez
authors.forename: Ma Teresa
authors.initials: MT
authors.lastname: Peña-Rangel
authors.forename: Juan R
authors.initials: JR
authors.lastname: Riesgo-Escovar
authors.forename: Alejandro
authors.initials: A
authors.lastname: Martínez-Martínez
authors.forename: Rocío
authors.initials: R
authors.lastname: Salceda
mesh_terms: D000818:Animals; D003571:Cytochalasin B / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000493:pharmacokinetics; D007328:Insulin / Q000494:pharmacology*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011894:Rana pipiens; D051381:Rats; D020318:Rats, Long-Evans; D012160:Retina / Q000187:drug effects* / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C506347:GLUT4 enhancer factor, rat; D007328:Insulin; D014157:Transcription Factors; D003571:Cytochalasin B; D051058:Oncogene Protein v-akt; D005947:Glucose