IDH3A and Cognitive impairment: Biochemical analyses have shown decreased activity of key enzymes controlling metabolic flux to the tricarboxylic acid (TCA) cycle—pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and isocitrate dehydrogenase—as well as changes in malic enzyme, a major anaplerotic component in neurons, parameters correlating with cognitive impairment [67–72].