Peripheral amyloid-ß clearance mediates cognitive impairment in non-alcoholic fatty liver disease.

ABSTRACT

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is a prevalent risk factor for cognitive impairment. Cerebral amyloid-ß (Aß) accumulation, as an important pathology of cognitive impairment, can be caused by impaired Aß clearance in the periphery. The liver is the primary organ for peripheral Aß clearance, but the role of peripheral Aß clearance in NAFLD-induced cognitive impairment remains unclear. METHODS: We examined correlations between NAFLD severity, Aß accumulation, and cognitive performance in female Sprague-Dawley rats. The impact of NAFLD on hepatic Aß clearance and the involvement of low-density lipoprotein receptor-related protein 1 (LRP-1) were assessed in rat livers and cultured hepatocytes. Additionally, a case-control study, including 549 NAFLD cases and 549 controls (782 males, 316 females), investigated the interaction between NAFLD and LRP-1 rs1799986 polymorphism on plasma Aß levels. FINDINGS: The severity of hepatic steatosis and dysfunction closely correlated with plasma and cerebral Aß accumulations and cognitive deficits in rats. The rats with NAFLD manifested diminished levels of LRP-1 and Aß in liver tissue, with these reductions inversely proportional to plasma and cerebral Aß concentrations and cognitive performance. In vitro, exposure of HepG2 cells to palmitic acid inhibited LRP-1 expression and Aß uptake, which was subsequently reversed by a peroxisome proliferator-activated receptor α (PPARα) agonist. The case-control study revealed NAFLD to be associated with an increment of 8.24% and 10.51% in plasma Aß40 and Aß42 levels, respectively (both P < 0.0001). Moreover, the positive associations between NAFLD and plasma Aß40 and Aß42 levels were modified by the LRP-1 rs1799986 polymorphism (P for interaction = 0.0017 and 0.0015, respectively). INTERPRETATION: LRP-1 mediates the adverse effect of NAFLD on peripheral Aß clearance, thereby contributing to cerebral Aß accumulation and cognitive impairment in NAFLD. FUNDING: Major International (Regional) Joint Research Project, National Key Research and Development Program of China, National Natural Science Foundation of China, and the Angel Nutrition Research Fund.