Abstract
Diabetes mellitus (DM) is now recognized as one of the risk factors for Alzheimer's disease (AD), and the disease-modifying effects of anti-diabetic drugs on AD have recently been attracting great attention. Sodium/glucose cotransporter 2 (SGLT2) inhibitors are a new class of anti-diabetic drugs targeting the SGLT2/solute carrier family 5 member 2 (SLC5A2) protein, which is known to localize exclusively in the brush border membrane of early proximal tubules in the kidney. However, recent data suggest that it is also expressed in other tissues. In the present study, we investigated the expression of SGLT2/SLC5A2 in human and mouse brains. Immunohistochemical staining of paraffin sections from autopsied human brains and C3H/He mouse brains revealed granular cytoplasmic immunoreactivity in choroid plexus epithelial cells and ependymal cells. Immunoblot analysis of the membrane fraction of mouse choroid plexus showed distinct immunoreactive bands at 70 and 26 kDa. Band patterns around 70 kDa in the membrane fraction of the choroid plexus were different from those in the kidney. Reverse transcription-polymerase chain reaction analysis confirmed the expression of Slc5a2 mRNA in the mouse choroid plexus. Our results provide in vivo evidence that SGLT2/SLC5A2 is expressed in cells facing the cerebrospinal fluid, in addition to early proximal tubular epithelial cells. These findings suggest that SGLT2 inhibitors may have another site of action in the brain. The effects of SGLT2 inhibitors on brain function and AD progression merit further investigation to develop better treatment options for DM patients.