MAPT and Alzheimer disease: In brains of AD patients, there was a negative correlation between on the one hand decreased GLUT-1 and -3 levels, decreased hypoxia-inducible factor 1-alpha (HIF-1α) and decreased O-GlcNAcylation and on the other hand hyper phosphorylation of tau protein and increased density of NFTs; concomitantly, the level of GLUT-2 was increased due to astrocyte activation [89].