GAPDH and Cognitive impairment: Proteomic studies have identified increased levels of the metabolism-related proteins lactate dehydrogenase B-chain (LDHB), pyruvate kinase (PKM), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in M4 Astrocyte in cerebrospinal fluid, which can be used as a biomarker for the early diagnosis of cognitive impairment (197).