3C). To determine the source of cholesterol, we assayed de novo cholesterol synthesis in Cyp7a1-tg mice. An increased bile acid pool should inhibit de novo cholesterol synthesis as observed in bile acid feeding experiments. However, hepatic de novo cholesterol synthesis rate was markedly increased by ∼11-fold (Fig. 3D), consistent with approximately seven-fold induction of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HmgCoAR) expression in Cyp7a1-tg mouse livers (Table 1). An increased bile acid pool normally should stimulate intestine fractional absorption of cholesterol. Surprisingly, we found that intestine fractional cholesterol absorption was similar between Cyp7a1-tg

mice and wild-type mice (Fig. 3E). These

results suggest that Cyp7a1-tg mice have http://www.selleckchem.com/products/jq1.html http://www.selleckchem.com/products/Maraviroc.html increased hepatic de novo cholesterol synthesis. Excess cholesterol is metabolized to bile acids, which are efficiently secreted into bile. Thus, the increased fecal cholesterol excretion in Cyp7a1-tg mice more likely resulted from increased biliary secretion of cholesterol rather than decreased intestine cholesterol absorption. Furthermore, plasma total cholesterol was decreased by 60% in Cyp7a1-tg mice, suggesting that increased hepatic cholesterol uptake may also contribute to hepatic cholesterol input. To investigate the mechanism of increased biliary bile acid and cholesterol secretion in Cyp7a1-tg mice, we first analyzed Hydroxychloroquine clinical trial messenger RNA (mRNA) expression of bile acid and cholesterol transporters in the liver and intestine. Cyp7a1-tg mice had significantly higher Abcg5 (2.7-fold) and Abcg8 (1.7-fold) mRNA expression in the liver, but not in the intestine (Table 1). Hepatic Abcg5/g8 protein levels were higher in Cyp7a1-tg mice than their wild-type littermates, whereas intestine Abcg5/g8 protein expression showed no difference (Fig. 4A). Expression of Sr-b1 mRNA increased 1.9-fold in Cyp7a1-tg mouse livers, but not in the intestine (Table 1). Expression of bile salt export pump (Bsep or Abcb11), a major biliary bile acid efflux transporter was significantly increased (1.7-fold) in Cyp7a1-tg mice (Table 1). Expression of liver sinusoidal

Na+-dependent taurocholate cotransport peptide (Ntcp), which reabsorbs bile salts from sinusoidal blood, did not change in Cyp7a1-tg mice. Expression of a hepatic phospholipid flipase (Abcb4) or multidrug resistance protein 2 (Mdr2), which is required for efficient biliary cholesterol secretion, did not change (Table 1). This is consistent with the observance of no significant increase of biliary phospholipid secretion in Cyp7a1-tg mice (Fig. 3C). In the intestine, mRNA expression levels of Niemann-Pick–like 1 protein (Npc1l1), which is an intestine cholesterol absorption transporter, and apical sodium-dependent bile salt transporter (Asbt), which reabsorbs bile salts from the lumen, were not changed in Cyp7a1-tg mice (Table 1).