OGDH and Alzheimer disease: Postmortem brain tissue isolated from AD patients displays reduced mitochondrial metabolic enzyme activity for pyruvate dehydrogenase (PDH) [45, 46], alpha-ketoglutarate dehydrogenase (α-KGDH) [46], isocitrate dehydrogenase (ICDH) [47], and complex IV or cytochrome-c-oxidase (COX) [48–50].