The incorporation and metabolism of amyloid-beta into chylomicron-like lipid emulsions.

The aggregation and deposition of amyloid-beta (Abeta) in the brain is thought to be an early event in the pathology of Alzheimer's disease (AD). Many studies have reported the association of Abeta with lipoproteins from plasma suggesting an involvement of lipoprotein particles in Abeta transport. Chylomicron-like lipid emulsions, resembling chylomicrons in composition, size and metabolism were prepared in the presence of [125I]Abeta1-40. Abeta was found to associate significantly with these lipid emulsions during their preparation. The chylomicron-like emulsions containing Abeta were then injected into a lateral ear vein of conscious rabbits and blood sampled at regular intervals up to 30 mins. It was observed that there was no difference in the plasma clearance of [125I]Abeta and that of the 3H-cholesteryl ester, a marker of the emulsion particles, demonstrating that Abeta remains associated with these particles throughout both their lipolysis and tissue uptake. Our results show that Abeta can be metabolised in association with triglyceride rich lipoproteins (TRLs). In addition we report the presence of specific markers of TRLs of hepatic and intestinal origin in human CSF thus suggesting a potential means of cerebral Abeta delivery.