The expression of the following factors was examined using immunofluorescence and western blot analysis at 0.5, 1, 2, 4 and 6 months after diabetes onset: hypoxia-inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), erythropoietin (EPO), erythropoietin receptor (EPOR), glial fibrillary acidic protein (GFAP), vimentin, glutamate-aspartate transporter (GLAST) and glutamine synthase (GS). Here, EPOR is linked to diabetes mellitus.