SR-BI- and ABCA1-mediated cholesterol efflux to serum from patients with Alagille syndrome

Abstract

Alagille syndrome is associated with bile duct paucity resulting in liver disease. Patients can be divided into mildly and severely icteric groups, with both groups having altered lipoproteins. The incidence of ischemic heart disease is rare in severely cholestatic children despite increased total cholesterol and decreased high density lipoprotein cholesterol (HDL-C). The present studies examine the impact of altered lipid and lipoproteins on scavenger receptor class B type I (SR-BI)- and ABCA1-mediated efflux to serum from both groups. Efflux was compared with serum from 29 patients (15 with normal plasma cholesteryl ester, 14 with low cholesteryl ester). Efflux via SR-BI and ABCA1 was studied using cell systems having either low or high expression levels of these receptors. SR-BI efflux was lower (P = 0.04) with serum from severely icteric patients (3.9 ± 1.4%) compared with serum from mildly icteric patients (5.1 ± 1.4%) and was positively correlated with HDL-C and its apolipoproteins. SR-BI-mediated efflux was not correlated with any particular mature HDL but was negatively correlated with small lipid-poor preβ-1 HDL. Consistent with severely icteric patients having high preβ-1 HDL levels, the ABCA1 efflux was significantly higher with their serum (4.8 ± 2.2%) compared with serum from mildly icteric patients (2.0 ± 0.6%) and was positively correlated with preβ-1 HDL.These studies demonstrated that preβ-1 HDL is the preferred acceptor for ABCA1 efflux, whereas many particles mediate SR-BI efflux.

Keywords

• high density lipoprotein
• scavenger receptor class B type I
• ATP binding cassette transporter 1