Single-nucleus transcriptional profiling of AD patient brains revealed significant metabolic abnormalities in astrocytes, particularly with glutamate Via downregulation of glutamine synthetase (GLUL) and glutamate dehydrogenase 1 (GLUD1), potentially disrupting the glutamate-glutamine cycle and leading to excitotoxicity [76]. Here, GLUD1 is linked to Alzheimer disease.