Mitochondrial Dysfunction in Alzheimer's Disease: Beyond Energy Failure Toward a Pathogenic Nexus

Mitochondrial dysfunction has gained recognition as a central and early event in the pathophysiology of Alzheimer's disease (AD), extending beyond classical energy failure to encompass complex and dynamic perturbations in organelle homeostasis. Despite extensive focus on amyloid-beta (Aβ) and tau, accumulating evidence implicates mitochondria as both targets and amplifiers of neurodegenerative cascades. This review provides a comprehensive synthesis of the mechanistic roles and therapeutic implications of mitochondrial dysfunction in AD, highlighting recent advances and emerging paradigms that underscore mitochondria as integrative nodes in disease onset, progression, and biomarker discovery.

We critically evaluate literature from molecular, cellular, and systemslevel studies-including postmortem brain tissue, transgenic models, and patient-derived cellsfocusing on key domains such as bioenergetic collapse, redox imbalance, mitochondrial dynamics and quality control, Aβ and tau interactions, calcium dysregulation, and apoptosis. Novel mitochondrial mechanisms such as mitochondria-associated membranes (MAMs), mitochondrial unfolded protein response (UPRmt), and mitonuclear communication are discussed alongside recent translational efforts.

Alzheimer's disease is characterized by widespread mitochondrial abnormalities, including impaired oxidative phosphorylation, increased reactive oxygen species (ROS), disrupted mitochondrial fission/fusion equilibrium, defective mitophagy, and abnormal calcium buffering. Moreover, direct mitochondrial accumulation of Aβ and tau disrupts protein import, respiratory chain integrity, and transport dynamics.

These dysfunctions synergistically activate caspase-mediated apoptotic pathways, exacerbating synaptic loss and neuronal death. Promising therapeutic avenues involve antioxidants, NAD+ precursors, mitophagy modulators, and MAM-targeted strategies. Concurrently, mitochondrial biomarkers such as circulating mtDNA, cytochrome c, and neuroimaging via 31P-MRS or PET are emerging as tools for early diagnosis and disease monitoring.

Mitochondria constitute a mechanistic nexus in AD, bridging upstream pathological triggers with downstream neurodegeneration. Advancing the field will require patient-specific models (e.g., iPSC-derived neurons, brain organoids), a deeper understanding of mitochondrial heterogeneity, and integration of mitochondrial targets into multi-modal therapeutic strategies. Precision mitochondrial medicine holds promise to transform AD management through mechanismbased diagnosis, stratification, and intervention.