Table 2.

Potential Causes of Reduced Cytochrome Oxidase Activity in Alzheimer’s Disease

Cause	Could apply to brain?	Could apply to non-brain tissues?	Could apply to cybrids?
Toxic inhibition by Aβ or another toxin	Yes	Yes	Probably not
Toxic downregulation by Aβ or another toxin	Yes	Yes	Probably not
Downregulation due to reduced synaptic activity	Yes	No	No
Nonspecific consequence of neurodegeneration	Yes	No	No
Nuclear gene mutation	Yes	Yes	Not unless it induces a diffuse accumulation of mtDNA mutation
mtDNA	Yes	Yes	Yes