Energetic crisis, mitochondrial vulnerability and disruption of lactate shuttle in Alzheimer's disease.

Alzheimer's disease (AD) has traditionally been characterized by amyloid-beta (Aβ) plaques and neurofibrillary tangles. Emerging evidence reveals that metabolic dysfunction represents a key pathological feature central to disease progression. Mitochondrial dysfunction in AD leads to impaired electron transport chain activity and reduced level of adenosine triphosphate (ATP) synthesis, preceding neurodegeneration and structural abnormalities in cognitive centres of the brain. Early glucose hypometabolism and lactate deprivation or interference with their utilization represent a primary bioenergetic failure driving mitochondrial dysfunction and neuroinflammation prior to the clinical manifestation of AD. While the brain relies on lactate as a prominent energy substrate, astrocytic metabolic defects lead to impaired neuronal energy homeostasis, thereby promoting neurodegeneration. In turn, this metabolic uncoupling could also be associated with defects in regenerative mechanisms by impairing adult neurogenesis in the hippocampus due to energy deprivation, accounting for memory deficits. This chapter discusses the evidence for the energetic crisis in AD, focusing on the disruption of the astrocyte-neuron lactate shuttle (ANLS), hypometabolism of glucose, and mitochondrial vulnerability, as interconnected pathogenic mechanisms. We emphasise cerebral bioenergetic metabolic failure as a central driver of cognitive decline, arising from irreversible reactive gliosis and neuroblastosis mechanisms and highlight various therapeutic options, including restoration of ANLS to mitigate the pathogenesis and memory loss in AD.