Abstract

OBJECTIVE:

Mutations in ATP-binding cassette transporter A1 (ABCA1), the cellular lipid transport molecule mutated in Tangier disease, result in the rapid turnover of high-density lipoprotein (HDL)-associated apolipoproteins that presumably are cleared by the kidneys. However, the role of ABCA1 in the liver for HDL apolipoprotein and cholesteryl ester (CE) catabolism in vivo is unknown.

METHODS AND RESULTS:

Murine HDL was radiolabeled with 125I in its apolipoprotein and with [3H]cholesteryl oleyl ether in its CE moiety. HDL protein and lipid metabolism in plasma and HDL uptake by tissues were investigated in ABCA1-overexpressing bacterial artificial chromosome (BAC)-transgenic (BAC+) mice and in mice harboring deletions of total (ABCA1-/-) and liver-specific ABCA1 (ABCA1(-L/-L)). In BAC+ mice with elevated ABCA1 expression, fractional catabolic rates (FCRs) of both the protein and the lipid tracer were significantly decreased in plasma and in the liver, yielding a diminished hepatic selective CE uptake from HDL. In contrast, ABCA1-/- or ABCA1(-L/-L) mice had significantly increased plasma and liver FCRs for both HDL tracers. An ABCA1 deficiency was associated with increased selective HDL CE uptake by the liver under all experimental conditions.

CONCLUSIONS:

Hepatic ABCA1 has a critical role for HDL catabolism in plasma and for HDL selective CE uptake by the liver.