Reduced Notch signaling in BBB vascular endothelial cells mediates high fat diet-induced alterations in brain glucose uptake and insulin signaling

Short term transition to high-fat diet (HFD) feeding causes rapid changes in the molecular architecture of the blood-brain-barrier (BBB), BBB permeability and brain glucose uptake. However, the precise mechanisms responsible for these changes remain elusive. Here we detected a rapid downregulation of Notch signaling after short-term HFD feeding. Conversely, Notch activation restores HFD-fed mouse serum induced reduction of Glut1 expression and glycolysis in cultured brain microvascular endothelial cells (BMECs). Selective, inducible expression of Notch-intracellular domain (IC) in BMECs prevents HFD-induced reduction of Glut1 expression and hypothalamic glucose uptake. Caveolin (Cav)-1 expression in BMECs is increased upon short term HFD feeding. However, NotchICBMECs mice display reduced caveola formation and BBB permeability. This ultimately translates into reduced hypothalamic insulin transport, action and systemic insulin sensitivity. Collectively, we highlight a critical role of Notch-signaling in the pleiotropic effects of short-term dietary transitions on BBB functionality. Overall design: We aimed at comparing a transcriptional signature of BBB VECs of animals exposed to control diet (CD) or high-fat diet (HFD) feeding for 3 days. To achieve that, we employed a genetically modified mouse model: Slco1c1-CreERT2, which expresses a tamoxifen-inducible variant of the Cre-recombinase under the control of Slco1c1 promoter specifically in BBB VECs. These animals were crossed with mice allowing for Cre-dependent expression of the ribosomal protein L10a with GFP. Mice expressing L10aGFP in BBB VECs were either fed a control or high fat diet for 3 days, hypothalami were dissected, GFP-tagged ribosomes precipitated and ribosome-associated RNA subjected to RNA sequencing. For cEND cells treated with WZB117: we aimed to investigate, whether the observed downregulation in Notch signaling could potentially represent acompensatory response to downregulated glucose transport and glycolysis in VECs of HFD-fed mice. To this end, we incubated cultured cEND cells with either vehicle or the Glut1 inhibitor WZB117 and subjected these cells to mRNA sequencing.