Modulating Insulin Signaling and Trafficking in Blood-Brain Barrier Endothelial Cells Using Lipid Nanoemulsions

Abstract

The compositionally distinct lipid rafts present in the plasma membrane regulates the restrictive trafficking and signal transduction in the blood-brain barrier (BBB) endothelium. Several devastating metabolic and neurodegenerative diseases are associated with lipid homeostasis disruption within the BBB endothelium. Here, we hypothesized that the delivery of lipid nanoemulsions containing unsaturated fatty acids (UFAs) provides a novel approach for disease modification by modulating lipid raft integrity and correcting the aberrant trafficking and signal transduction. Western blot and flow cytometry analysis showed that soybean oil nanoemulsions (SNEs) containing polyunsaturated fatty acids (PUFAs) increased insulin uptake and phospo-AKT (p-AKT) expression, which is a marker for the stimulation of metabolic arm of the insulin signaling, in human cerebral microvascular endothelial cell line (hCMEC/D3) monolayers. Moreover, the use of Alex Fluor 647 labelled cholera toxin (AF647-CXT) in polarized hCMEC/D3 cell monolayers demonstrated that SNEs alter lipid raft morphology, which highlights the role of PUFAs-enriched SNEs in the regulation of lipid rafts. However, olive oil nanoemulsions (ONEs) containing monounsaturated fatty acids (MUFAs) had no detectable impact on lipid raft integrity, AKT phosphorylation, or insulin uptake. These findings provided direct evidence that nanoemulsions containing PUFAs can upregulate the insulin-pAKT pathway and facilitate insulin trafficking at the BBB. Therefore, SNEs may provide a novel nano-strategy to modulate cerebrovascular function in metabolic and neurodegenerative diseases.