Modulating insulin signaling and trafficking at the blood-brain barrier endothelium using lipid based nanoemulsions

The compositionally distinct lipid rafts present in the plasma membrane regulate the restrictive trafficking and signal transduction in the blood-brain barrier (BBB) endothelium. Several metabolic and neurodegenerative diseases are associated with lipid homeostasis disruption within the BBB endothelium. Here, we hypothesized that the delivery of lipid triglyceride based nanoemulsions containing unsaturated fatty acids (UFAs) provides a novel non-pharmacological approach to modulate lipid raft integrity and rectify the aberrant trafficking and signal transduction. The current study has shown that soybean oil nanoemulsions (SNEs) altered the morphology of lipid rafts that are stained by Alex Fluor 647 labelled cholera toxin (AF647-CTX) in polarized human cerebral microvascular endothelial (hCMEC/D3) cell monolayers. Moreover, western blot and flow cytometry analysis showed that SNEs containing polyunsaturated fatty acids (PUFAs) increased phospo-AKT (p-AKT) expression, a marker for the stimulation of metabolic arm of insulin signaling, and insulin uptake in hCMEC/D3 monolayers. 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 SNEs containing PUFAs can upregulate insulin-pAKT pathway, facilitate insulin trafficking at the BBB, and potentially address cerebrovascular dysfunction in metabolic and neurodegenerative diseases.