AQP1 and type 2 diabetes mellitus: IF staining revealed lower levels of glutathione peroxidase 4 (GPX4), a marker of ferroptosis, in PT (AQP1) of db/db mice than those in db/m mice, and immunohistochemistry (IHC) stain also found decreased GPX4 level in the PT (AQP1) of the T2D patient compared to the normal individual (Fig. 3K, L).