GAD1 and Alzheimer disease: Our current findings of increased glutamate and decreased GABA levels are consistent with a previously-reported decrease in glutamate decarboxylase 1 (GAD1 brain; EC 4.1.1.15), the enzyme responsible for conversion of glutamate to GABA in the AD-brain [44], and increased glutamate in the CSF of patients with AD [42], [45].