Bridging systemic metabolic dysfunction and Alzheimer's disease: the liver interface.

Alzheimer's disease (AD) is increasingly recognized as a systemic disorder with a substantial metabolic disorder component, where the liver significantly impacts the brain via the liver-brain axis. Key mechanisms include the liver's role in clearing peripheral β-amyloid (Aβ), the influence of hepatic enzymes and metabolites on cognitive decline, and the systemic effects of metabolic disorders on AD progression. Hepatokines, liver-secreted proteins including fibroblast growth factor (FGF)-21, selenoprotein P (SELENOP), Fetuin-A, Midbrain astrocyte-derived neurotrophic factor (MANF), apolipoprotein J (ApoJ), sex hormone-binding globulin (SHBG), Adropin and Angiopoietin-like protein 3 (ANGPTL3), could regulate insulin sensitivity, lipid metabolism, oxidative stress, immune responses, and neurotrophic support. These pathways are closely linked to core AD pathologies, including Aβ aggregation, tau hyperphosphorylation, neuroinflammation, oxidative stress and mitochondrial dysfunction. Lifestyle interventions, including exercise and dietary modifications, that regulate hepatokines expression may offer novel preventive and therapeutic strategies for AD. This review synthesizes current knowledge on the liver-brain crosstalk in AD, emphasizing the mechanistic role of liver in bridging metabolic dysfunction with neurodegeneration and underscores the diagnostic and therapeutic potential of hepatokines in addressing AD's complex pathology.