Mitochondria and cell bioenergetics: increasingly recognized components and a possible etiologic cause of Alzheimer's disease.

SIGNIFICANCE: Mitochondria and brain bioenergetics are increasingly thought to play an important role in Alzheimer's disease (AD). RECENT ADVANCES: Data that support this view are discussed from the perspective of the amyloid cascade hypothesis, which assumes beta-amyloid perturbs mitochondrial function, and from an opposite perspective that assumes mitochondrial dysfunction promotes brain amyloidosis. A detailed review of cytoplasmic hybrid (cybrid) studies, which argue mitochondrial DNA (mtDNA) contributes to sporadic AD, is provided. Recent AD endophenotype data that further suggest an mtDNA contribution are also summarized. CRITICAL ISSUES AND FUTURE DIRECTIONS: Biochemical, molecular, cybrid, biomarker, and clinical data pertinent to the mitochondria-bioenergetics-AD nexus are synthesized and the mitochondrial cascade hypothesis, which represents a mitochondria-centric attempt to conceptualize sporadic AD, is discussed.