Pruritus is a seriously disabling symptom accompanying many cholestatic liver disorders. Recent experimental evidence implicated the lysophospholipase, autotaxin (ATX), and its product, lysophosphatidic acid (LPA), as potential mediators of cholestatic pruritus. In this study, we highlight that increased serum ATX levels are specific for pruritus of cholestasis, but not pruritus of uremia, Hodgkin's disease, or atopic dermatitis. Treatment of patients with cholestasis with the bile salt sequestrant, colesevelam, but not placebo, effectively reduced total serum bile salts and fibroblast growth factor 19 levels, but only marginally altered pruritus intensity and ATX activity. Rifampicin (RMP) significantly reduced itch intensity and ATX activity in patients with pruritus not responding to bile salt sequestrants. In vitro , RMP inhibited ATX expression in human HepG2 hepatoma cells and hepatoma cells overexpressing the pregnane X receptor (PXR), but not in hepatoma cells in which PXR was knocked down. Treatment of severe, refractory pruritus by the molecular adsorbents recirculation system or nasobiliary drainage improved itch intensity, which, again, correlated with the reduction of ATX levels. Upon reoccurrence of pruritus, ATX activity returned to pretreatment values. Conclusion : Serum ATX activity is specifically increased in patients with cholestatic, but not other forms of, systemic pruritus and closely correlates with the effectiveness of therapeutic interventions. The beneficial antipruritic action of RMP may be explained, at least partly, by the PXR-dependent transcriptional inhibition of ATX expression. Thus, ATX likely represents a novel therapeutic target for pruritus of cholestasis. (Hepatology 2012)

ApoAV has been discovered recently as a novel modifier of triglyceride (TG) metabolism, but the pathways involved are currently unknown. To gain insight into the function of apoAV, adenovirus-mediated gene transfer of murine apoa5 to C57Bl/6 mice was employed. The injection of low doses of Ad-apoa5 (1-5 x 10(8) plaqueforming units/mouse) dose-dependently reduced plasma very low density lipoprotein (VLDL)-TG levels. First, we evaluated whether a reduced hepatic VLDL production contributed to the TG-lowering effect. Ad-apoa5 treatment dose-dependently diminished (29-37%) the VLDL-TG production rate without affecting VLDL particle production, suggesting that apoAV impairs the lipidation of apoB. Second, Ad-apoa5 treatment dose-dependently reduced (68-88%) the postprandial hypertriglyceridemia following an intragastric fat load, suggesting that apoAV also stimulates the lipoprotein lipase (LPL)-dependent clearance of TG-rich lipoproteins. Indeed, recombinant apoAV was found to dose-dependently stimulate LPL activity up to 2.3-fold in vitro. Accordingly, intravenously injected VLDL-like TG-rich emulsions were cleared at an accelerated rate concomitant with the increased uptake of emulsion TG-derived fatty acids by skeletal muscle and white adipose tissue in Ad-apoa5-treated mice. From these data, we conclude that apoAV is a potent stimulator of LPL activity. Thus, apoAV lowers plasma TG by both reducing the hepatic VLDL-TG production rate and by enhancing the lipolytic conversion of TG-rich lipoproteins.

Fibroblast growth factor 19 (FGF19) is an endocrine factor produced by the small intestine in response to uptake of luminal bile salts. In the liver, FGF19 binds to FGF receptor-4, resulting in down-regulation of cytochrome P (CYP) 7A1 and reduced bile salt synthesis. Down-regulation of CYP7A1 under cholestatic conditions has been attributed to bile salt–mediated induction of the transcriptional repressor short heterodimer partner (SHP), because the interrupted enterohepatic cycle of bile salts is thought to abrogate intestinal FGF19 production and thus result in lowering of plasma FGF19 levels. Unexpectedly, we observed marked elevation of plasma FGF19 in patients with extrahepatic cholestasis caused by a pancreatic tumor (2.3 ± 2.3 in cholestatic versus 0.40 ± 0.25 ng/mL and 0.29 ± 0.12 ng/mL in postcholestatic patients who received preoperative drainage by biliary stenting, P = 0.004, and noncholestatic control patients, P = 0.04, respectively). Although FGF19 messenger RNA (mRNA) is virtually absent in normal liver, FGF19 mRNA was strongly increased (31-fold to 374-fold, P < 0.001) in the liver of cholestatic patients in comparison with drained and control patients. In the absence of changes in SHP mRNA, CYP7A1 mRNA was strongly reduced (7.2-fold to 24-fold, P < 0.005) in the liver of cholestatic patients in comparison with drained and control patients, indicating an alternative regulatory pathway. Alterations in transcripts encoding hepatobiliary transporters [adenosine triphosphate–binding cassette, subfamily C, member 3 (ABCC3)/multidrug resistance protein 3 (MRP3), organic solute transporter α/β (OSTα/β), organic anion-transporting polypeptide (OATP1B1)] further suggest that bile salts are secreted via a nonbiliary route in patients with extrahepatic cholestasis. Conclusion: The liver expresses FGF19 under conditions of extrahepatic cholestasis. This is accompanied by a number of adaptations aimed at protecting the liver against bile salt toxicity. FGF19 signaling may be involved in some of these adaptations. (Hepatology 2009.)

Following birth, the neonatal intestine is exposed to maternal and environmental bacteria that successively form a dense and highly dynamic intestinal microbiota. Whereas the effect of exogenous factors has been extensively investigated, endogenous, host-mediated mechanisms have remained largely unexplored. Concomitantly with microbial colonization, the liver undergoes functional transition from a hematopoietic organ to a central organ of metabolic regulation and immune surveillance. The aim of the present study was to analyze the influence of the developing hepatic function and liver metabolism on the early intestinal microbiota. Here, we report on the characterization of the colonization dynamics and liver metabolism in the murine gastrointestinal tract (n = 6–10 per age group) using metabolomic and microbial profiling in combination with multivariate analysis. We observed major age-dependent microbial and metabolic changes and identified bile acids as potent drivers of the early intestinal microbiota maturation. Consistently, oral administration of tauro-cholic acid or β-tauro-murocholic acid to newborn mice (n = 7–14 per group) accelerated postnatal microbiota maturation.