OGA and Alzheimer disease: In neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), dysregulated expression of OGT and OGA in the brain leads to abnormal O‐GlcNAcylation levels, resulting in functional impairment of neuronal proteins and cellular damage [28].