Metabolic Drivers of Alzheimer's Disease: Integrating brain Hypometabolism, insulin Resistance, and systemic dysregulation.

The repeated failure of amyloid therapies highlights a core misunderstanding of Alzheimer's disease (AD) origins. A new metabolic paradigm now positions impaired brain metabolism-not protein accumulation-as the central, early driver. Key evidence shows cerebral glucose hypometabolism emerges decades before symptoms, linked to brain insulin resistance ("type 3 diabetes") and mitochondrial dysfunction. The APOE ε4 allele worsens lipid defects thereby, accelerating the progression of AD pathology. These disruptions-alongside gut-brain axis issues-create a self-reinforcing cycle that fuels amyloid β (Aβ), tau, neuroinflammation, and synaptic loss. This framework integrates with the neuron-centric model, explaining disease heterogeneity and the inadequacy of single-target drugs. This review particularly highlights the metabolic perspective in AD, underscoring the need for a radical therapeutic shift: from late stage protein clearance strategies to early, multimodal interventions that restore metabolic homeostasis and disrupt the entire pathogenic continuum.