Furthermore, several studies performed in MCI patients and early AD patients have shown that decreased glucose transporter 1 (GLUT1) expression suppresses glucose transport through the BBB prior to brain atrophy, neurodegenerative manifestations, or conversion to AD, leading to impaired local glucose uptake, which in turn causes inadequate neuronal energy sources (Simpson et al., 1994; Winkler et al., 2015). Here, SLC2A1 is linked to Alzheimer disease.