Our data provide a model in which miR-23b miRNAs repress bile duct gene expression in fetal hepatocytes while promoting their growth by down-regulating Smads and consequently TGFbeta signaling. Concomitantly, low levels of the miR-23b miRNAs are needed in cholangiocytes to allow TGFbeta signaling and bile duct formation.

No abstract

Bile duct morphogenesis involves sequential induction of biliary specific gene expression, bilayer generation, cell proliferation, remodeling and apoptosis. HBC-3 cells are a model system to study differentiation of hepatoblasts along the hepatocytic or bile ductular lineage in vitro and in vivo. We used microarray to define molecular pathways during ductular differentiation in response to Matrigel. The temporal pattern of expression of marker genes induced was similar to that observed during bile duct formation in vivo. Notch, HNF1beta, Polycystic kidney disease 2, Bicaudal C 1 and beta-catenin were up regulated during the time course. Functional clustering analysis revealed significant up regulation of clusters of genes involved in extracellular matrix remodeling, ion transport, vacuoles, lytic vacuoles, pro-apoptotic and anti-apoptotic genes, transcription factors and negative regulators of the cell proliferation, while genes involved in the cell cycle were significantly down regulated. Notch signaling pathway was activated by treatment with Matrigel. In addition, TGFbeta/BMP signaling pathway members including the type I TGFbeta receptor and Smads 3, 4 and 5 were significantly up regulated, as were several TGFbeta/BMP responsive genes including Hey 1, a regulator of Notch pathway signaling. SMADS 3, 4 and 5 were present in the nuclear fraction of HBC-3 cells during ductular differentiation in vitro, but not during hepatocyte differentiation. SMAD 5 was preferentially expressed in hepatoblasts undergoing bile duct morphogenesis in the fetal liver, while the TGFbeta/BMP signaling antagonist chordin, was expressed throughout the liver suggesting a mechanism by which TGFbeta/BMP signaling is limited to hepatoblasts that contact portal mesenchyme in vivo.

Anacetrapib is an inhibitor of cholesteryl ester transfer protein (CETP), associated with reduction in LDL cholesterol and increase in HDL cholesterol in hypercholesterolemic patients. Anacetrapib was not taken forward into filing/registration as a new drug for coronary artery diease, despite the observation of a ∼9% reduction in cardiovascular risk in a large phase III cardiovascular outcomes trial (REVEAL). Anacetrapib displayed no adverse effects throughout extensive preclinical safety evaluation, and no major safety signals were observed in clinical trials studying anacetrapib, including REVEAL. However, anacetrapib demonstrated a long terminal half-life in all species, thought to be due, in part, to distribution into adipose tissue. We sought to understand the dependence of anacetrapib's long half-life on adipose tissue and to explore potential mechanisms that might contribute to the phenomenon. In mice, anacetrapib localized primarily to the lipid droplet of adipocytes in white adipose tissue; in vitro, anacetrapib entry into cultured human adipocytes depended on the presence of a mature adipocyte and lipid droplet but did not require active transport. In vivo, the entry of anacetrapib into adipose tissue did not require lipase activity, as the distribution of anacetrapib into adipose was-not affected by systemic lipase inhibition using poloaxamer-407, a systemic lipase inhibitor. The data from these studies support the notion that the entry of anacetrapib into adipose tissue/lipid droplets does not require active transport, nor does it require mobilization or entry of fat into adipose via lipolysis.