Figure 9. Schematic model of precocious enhancement of GLUT5 expression in suckling pups by Dex.

In suckling pups after Dex (D) injection, Dex binds to the GR in the cytosol and then the Dex–GR complex translocates to the nucleus to stimulate (+) the synthesis of a GR-sensitive intermediate/s (GR-I(s)). This intermediate then allows fructose to stimulate GLUT5 either directly, for example as a cofactor binding to the GLUT5 promoter, or indirectly for example, as a cytoplasmic precursor inducing aggregation of transcription factors required for GLUT5 synthesis. While it seems clear that the effect of Dex on GLUT5 is indirect requiring fructose and at least one intermediate, it is not clear whether GR is again involved (?) in inducing GLUT5 transcription by binding to one or more GR response elements (GRE) identified in the GLUT5 promoter region.