Lrp1 and Abcb1 are two important transporters responsible for Aβ efflux across the BBB.57,58 Depletion or inhibition of endothelial Lrp1 and Abcb1 leads to Aβ accumulation in the AD mouse brain.76,77 Since transportation of Aβ from brain parenchyma to peripheral plasma might contribute 25% of total clearance of cerebral Aβ,56 Aβ efflux represents a major pathway mediating the reduction of Aβ in the brain of AD mice following depletion of gut bacteria. This evidence concerns the gene ABCB1 and Alzheimer disease.