01) and the cholesterol half-transporters Abcg5 and Abcg8 were decreased (P < 0.01 for both) (Table 2). ApoE overexpression reduced expression of the key enzyme for the alternative bile acid synthesis pathway in the liver, Cyp27a1 (P < 0.01) and the enzyme responsible for cholate synthesis, Cyp8b1 (P < therefore 0.05) but did not affect expression of the rate-limiting enzyme for classic bile acid synthesis, Cyp7a1 (Table 2). Hepatic gene expression of the sterol regulatory binding protein 2 (Srebp2) was suppressed by apoE overexpression (P < 0.05), whereas mRNA expression of its two target genes LDL receptor (Ldlr) and the rate-limiting enzyme for cholesterol synthesis, HMG-CoA reductase (Hmgcr), was not significantly affected (Table 2). There was also no difference in Abca1 mRNA levels in the liver between AdhApoE3 injected wild-type mice and controls.

In hCETP tg mice, virtually identical changes in liver gene expression were found in response to apoE overexpression (Supplementary Table III). Consistent with unaltered biliary secretion of cholesterol and bile acids in wild-type mice, the fecal mass output of neutral sterols (3.11 �� 0.22 vs. 2.49 �� 0.34 ��mol/day; Supplementary Table IV) and bile acids (2.33 �� 0.19 vs. 2.65 �� 0.11 ��mol/day; Supplementary Table V) was not influenced by overexpression of apoE. Likewise, hCETP tg mice injected with AdhApoE3 also excreted similar amounts of neutral sterols (Supplementary Table IV) and bile acids (Supplementary Table V) into the feces compared with AdNull administered controls.

Taken together, these results indicate that apoE overexpression promotes hepatic cholesterol uptake without increasing biliary and fecal sterol excretion. Hepatic apoE overexpression does not affect macrophage-to-feces RCT Because apoE overexpression increased hepatic selective uptake via SR-BI, an important step in the RCT pathway, but did not influence mass biliary and fecal sterol excretion, we next investigated whether apoE overexpression might affect overall RCT. In vivo RCT was traced after intraperitoneal injection of primary mouse macrophages loaded with 3H-cholesterol in control and apoE-overexpressing wild-type mice. The appearance of tracer in plasma was not significantly different between controls and mice injected with AdhApoE3 at 6 h (2.1 �� 0.6 vs. 3.0 �� 0.5% injected tracer dose; n.s.), 24 h (2.8 �� 0.4 vs. 2.

8 �� 0.3% injected tracer dose; n.s.), and 48 h (2.3 �� 0.2 vs. 2.4 �� 0.2% injected tracer dose; n.s.) after macrophage injection (Fig. 3A). Although apoE overexpression led to a 63% increase in macrophage-derived 3H-cholesterol within the liver (7.0 �� 0.9 vs. 11.3 �� 1.2% injected tracer dose; P < 0.05; Fig. 3B), overall, in vivo RCT remained essentially Anacetrapib unchanged as reflected by no effect on the total excretion of 3H-tracer into the feces (10.