MCAT and Alzheimer disease: The other MT-DLOOP variant (194) showed interactions with variants in genes of Complexes I, III, IV and V (MT-ND4, MT-CYB, MT-COX3 and MT-ATP8, respectively); the joint presence of certain genotypes of these variants may affect the levels of TAU in CSF for individuals with MCI, increasing these levels, a trend seen for the investigated AD cases.