Mitochondrial Dysfunction-Mediated Neurodegeneration in Alzheimer's Disease

This hypothesis proposes that mitochondrial dysfunction represents a primary pathogenic mechanism in Alzheimer’s disease, operating through impaired ATP synthesis and increased oxidative stress that precedes and drives amyloid-beta accumulation. Specifically, mutations or age-related damage to TFAM (Transcription Factor A, Mitochondrial) lead to defective mitochondrial DNA replication and reduced expression of respiratory chain complexes I and IV. This mitochondrial impairment creates a bioenergetic crisis in neurons, particularly affecting synaptic transmission which requires high ATP levels. The resulting energy deficit triggers compensatory upregulation of APP processing through the amyloidogenic pathway as neurons attempt to maintain cellular homeostasis. Additionally, dysfunctional mitochondria generate excessive reactive oxygen species, which directly damage tau proteins leading to hyperphosphorylation and neurofibrillary tangle formation. The mitochondrial calcium buffering capacity becomes compromised, resulting in cytosolic calcium dysregulation that further exacerbates tau pathology and synaptic dysfunction. This creates a vicious cycle where mitochondrial damage promotes both hallmark pathologies of Alzheimer’s disease. The hypothesis predicts that therapeutic interventions targeting mitochondrial biogenesis through TFAM overexpression or mitochondrial antioxidants would be more effective than amyloid-targeting therapies, particularly in early-stage disease. Evidence would include demonstrating mitochondrial abnormalities in presymptomatic individuals, showing TFAM deficiency correlates with disease progression, and proving that mitochondrial-targeted interventions prevent downstream amyloid and tau pathologies in cellular and animal models.