Activities of TCA cycle enzymes in brains from patients with autopsy-confirmed AD and clinical dementia ratings (CDRs) before death have been measured, and significant (p <0.01) decreases in the activities of the PDH complex, IDH, and the DLD complex, and increases in SDH and MDH were reported (Bubber et al., 2005). The gene discussed is DLD; the disease is Alzheimer disease.