Assessing the critical role of ceramide in the pathogenesis of Alzheimer's disease and its clinical significance.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by amyloid-β (Aβ) deposition, tau hyperphosphorylation, and synaptic loss. Emerging evidence indicates that apolipoprotein E (APOE) polymorphism and dysregulated ceramide metabolism are critical links among these pathogenic processes. Ceramide accumulation in the brain contributes to Aβ generation, tau phosphorylation, and neuronal apoptosis. Elevated ceramide levels have been observed in plasma, cerebrospinal fluid, and peripheral organs such as the liver, reflecting systemic lipid dysregulation. Lipoproteins-particularly low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL)-transport ceramide across the blood-brain barrier, while apoE4 isoforms exacerbate this process by disrupting vascular integrity and lipid homeostasis. In addition, hepatic and gut-derived ceramides may influence neurodegeneration through the liver-gut-brain axis. Therapeutic interventions targeting ceramide synthesis (serine palmitoyltransferase inhibitors), production (neutral sphingomyelinase inhibitors), and the ceramide/sphingosine-1-phosphate (S1P) balance show potential in preclinical models for reducing Aβ pathology, tau aggregation, and neuroinflammation. These findings position ceramide metabolism as a critical mediator of AD pathogenesis and a promising target for diagnosis and treatment. Modulating ceramide and S1P signaling could complement current amyloid- and tau-directed therapies, offering new opportunities for disease modification and early intervention.