Downregulation of LRP1 [correction of LPR1] at the Blood-brain Barrier in Streptozotocin-induced Diabetic Mice

Deposition of amyloid-beta peptide (Abeta) in the diabetic brain is poorly understood. Low-density lipoprotein receptor related protein 1(LRP1) at the blood-brain barrier (BBB) is critical for regulation of Abeta homeostasis in the brain. In this study, we used streptozotocin-induced diabetic mice to observe the expression of LRP1 at the BBB by Western blot and immunocytochemical analysis, and to study in vivo brain-to-blood efflux transport of 125I-Abeta1-40 using brain clearance studies. In the diabetic mice with hyperglycemia (>16.0 mmol/l) at 6 weeks, LRP1 expression at the BBB was significantly downregulated; no significant changes of LRP1 levels were found at 1 and 3 weeks after diabetes induction. The data of brain clearance studies for Abeta showed significant decrease in LRP1-dependent transport of Abeta across the BBB at 6 weeks after diabetes induction, while no significant changes of LRP1-dependent transport of Abeta across the BBB at 1 or 3 weeks after diabetes induction were apparent. We conclude that the downregulation of LRP1 at the BBB contributes to cerebral Abeta deposition in diabetes mellitus.