Excretion of Amyloid-β in the Gastrointestinal Tract and Regulation by the Gut Microbiota

Amyloid-β (Aβ) is important in the etiology of Alzheimer's disease (AD). Removal of Aβ from the brain is a major strategy for the prevention and treatment of AD.To clarify whether Aβ42 can be cleared by intestinal excretion and whether the gut microbiota (GM) can affect the excretory clearance of Aβ42 in the peripheral blood and intestines.Male 8-month-old C57BL6 mice were maintained on either normal chow or received broad-spectrum antibiotics in their drinking water for one week. Sterile saline, fluorescein isothiocyanate (FITC), or FITC-Aβ42 (fluorescein isothiocyanate-labeled amyloid-β42 peptides) was injected 1 h before sampling. Related changes of Aβ42 before and after injection were evaluated.FITC-Aβ42 was injected into mice through the tail vein and could later be detected in feces. Furthermore, the fecal concentrations of FITC-Aβ42 were higher in mice that had been fed antibiotics to alter their GM than in normal mice. However, the FITC-Aβ42 concentrations in blood showed the opposite pattern.Aβ42 can be excreted into the intestinal lumen and is regulated by the GM.