Dysregulated Lipid Metabolism and Neurovascular Unit Dysfunction: Novel Mechanisms Linking Alzheimer's Disease and Vascular Dementia.

The neurovascular unit (NVU) represents a multicellular functional ensemble pivotal to the preservation of cerebral homeostasis, encompassing endothelial cells, pericytes, glial cells (astrocytes, microglia, oligodendrocytes), and neurons. This complex orchestrates the regulation of blood-brain barrier (BBB) integrity, cerebral blood flow (CBF), and the metabolic microenvironment requisite for neuronal viability and functional competence. Accumulating lines of evidence have underscored that NVU dysfunction constitutes a critical early pathological event in neurodegenerative disorders, including Alzheimer's disease (AD) and vascular dementia (VaD). The present review summarizes the structural composition and core physiological functionalities of the NVU, with particular emphasis on the emerging role of lipid metabolism dysregulation in mediating NVU impairment-an aberrant process encompassing lipid droplets, apolipoprotein E (APOE), ATPase phospholipid transporting 11B (ATP11B), triggering receptor expressed on myeloid cells 2 (TREM2), and ATP-binding cassette (ABC) transporters. We further delineate the mechanisms by which disrupted lipid homeostasis elicits neuroinflammation, amplifies oxidative stress, impairs amyloid-β (Aβ) clearance, and precipitates BBB breakdown, ultimately culminating in cognitive decline. Simultaneously, this review examines controversies within the field, such as the specific role of apolipoprotein E ε4 allele (APOE4) in disease and highlights the significant pathophysiological differences between preclinical animal models and human diseases. Therapeutic strategies targeting lipid metabolism or the blood-brain barrier still face considerable challenges in clinical translation. Meanwhile, emerging tools such as lipidomics contribute to systematically analyzing the associated dysregulated lipid networks, thereby aiding in the identification of novel therapeutic targets.