Insulin-sensitive GLUT4 glucose transporters are colocalized with GLUT3-expressing cells and demonstrate a chemically distinct neuron-specific localization in rat brain

Abstract

The insulin-sensitive glucose transporter (GLUT) 4, expressed primarily in peripheral tissue, has recently been detected also in the brain, demonstrating a region-specific distribution. To identify the chemical nature of neurons expressing GLUT4 and to disclose whether GLUT4-containing neurons also express the GLUT3 isoform, combined in situ hybridization for GLUT3 mRNA and double-labeling immunocytochemistry for GLUT4 and different cellular markers was performed in brain sections through rat basal forebrain, cerebral cortex, hippocampus, and cerebellum. In all brain regions examined, GLUT4 immunoreactivity was exclusively found in neurons, and GLUT4-immunoreactive cells were colocalized with neurons expressing GLUT3 mRNA. In rat basal forebrain, cholinergic and parvalbumin-containing gamma-aminobutyric acid-ergic cells demonstrated GLUT4 immunoreactivity, whereas calretinin-, calbindin-D-, and neuronal nitric oxide synthase-containing neurons did not express GLUT4 protein. Because brain GLUT4 transporters have been suggested to play a role in rapidly providing additional glucose to neurons under conditions of high-energy demand, the selective presence of GLUT4 in basal forebrain cholinergic cells may explain the specific vulnerability of these cells to a lack of glucose supply.