Objective Fibroblast growth factor 15/19 (FGF15/19), an enterokine that regulates synthesis of hepatic bile acids (BA), has been proposed to influence fat metabolism. Without FGF15/19, mouse liver regeneration after partial hepatectomy (PH) is severely impaired. We studied the role of FGF15/19 in response to a high fat diet (HFD) and its regulation by saturated fatty acids. We developed a fusion molecule encompassing FGF19 and apolipoprotein A-I, termed Fibapo, and evaluated its pharmacological properties in fatty liver regeneration. Design Fgf15−/− mice were fed a HFD. Liver fat and the expression of fat metabolism and endoplasmic reticulum (ER) stress-related genes were measured. Influence of palmitic acid (PA) on FGF15/19 expression was determined in mice and in human liver cell lines. In vivo half-life and biological activity of Fibapo and FGF19 were compared. Hepatoprotective and proregenerative activities of Fibapo were evaluated in obese db/db mice undergoing PH. Results Hepatosteatosis and ER stress were exacerbated in HFD-fed Fgf15 −/− mice. Hepatic expression of Pparγ2 was elevated in Fgf15 −/− mice, being reversed by FGF19 treatment. PA induced FGF15/ 19 expression in mouse ileum and human liver cells, and FGF19 protected from PA-mediated ER stress and cytotoxicity. Fibapo reduced liver BA and lipid accumulation, inhibited ER stress and showed enhanced half-life. Fibapo provided increased db/db mice survival and improved regeneration upon PH. Conclusions FGF15/19 is essential for hepatic metabolic adaptation to dietary fat being a physiological regulator of Pparγ2 expression. Perioperative administration of Fibapo improves fatty liver regeneration.

Genome instability is related to disease development and carcinogenesis. DNA lesions are caused by genotoxic compounds but also by the dysregulation of fundamental processes like transcription, DNA replication and mitosis. Recent evidence indicates that impaired expression of RNA-binding proteins results in mitotic aberrations and the formation of transcription-associated RNA–DNA hybrids (R-loops), events strongly associated with DNA injury. We identify the splicing regulator SLU7 as a key mediator of genome stability. SLU7 knockdown results in R-loops formation, DNA damage, cell-cycle arrest and severe mitotic derangements with loss of sister chromatid cohesion (SCC). We define a molecular pathway through which SLU7 keeps in check the generation of truncated forms of the splicing factor SRSF3 (SRp20) (SRSF3-TR). Behaving as dominant negative, or by gain-of-function, SRSF3-TR impair the correct splicing and expression of the splicing regulator SRSF1 (ASF/SF2) and the crucial SCC protein sororin. This unique function of SLU7 was found in cancer cells of different tissue origin and also in the normal mouse liver, demonstrating a conserved and fundamental role of SLU7 in the preservation of genome integrity. Therefore, the dowregulation of SLU7 and the alterations of this pathway that we observe in the cirrhotic liver could be involved in the process of hepatocarcinogenesis.

Canalicular bile is modified along bile ducts through reabsorptive and secretory processes regulated by nerves, bile salts, and hormones such as secretin. Secretin stimulates ductular cystic fibrosis transmembrane conductance regulator (CFTR)-dependent Cl ؊ efflux and subsequent biliary HCO 3 ؊ secretion, possibly via Cl ؊ /HCO 3 ؊ anion exchange (AE). However, the contribution of secretin to bile regulation in the normal rat, the significance of choleretic bile salts in secretin effects, and the role of Cl ؊ /HCO 3 ؊ exchange in secretin-stimulated HCO 3 ؊ secretion all remain unclear. Here, secretin was administered to normal rats with maintained bile acid pool via continuous taurocholate infusion. Bile flow and biliary HCO 3 ؊ and Cl ؊ excretion were monitored following intrabiliary retrograde fluxes of saline solutions with and without the Cl ؊ channel inhibitor 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) or the Cl ؊ /HCO 3 ؊ exchange inhibitor 4,4 -diisothiocyanatostilbene-2,2 -disulfonic acid (DIDS). Secretin increased bile flow and biliary excretion of HCO 3 ؊ and Cl ؊ . Interestingly, secretin effects were not observed in the absence of taurocholate. Whereas secretin effects were all blocked by intrabiliary NPPB, DIDS only inhibited secretin-induced increases in bile flow and HCO 3 ؊ excretion but not the increased Cl ؊ excretion, revealing a role of biliary Cl ؊ /HCO 3 ؊ exchange in secretininduced, bicarbonate-rich choleresis in normal rats. Finally, small hairpin RNA adenoviral constructs were used to demonstrate the involvement of the Na ؉ -independent anion exchanger 2 (AE2) through gene silencing in normal rat cholangiocytes. AE2 gene silencing caused a marked inhibition of unstimulated and secretin-stimulated Cl ؊ /HCO 3 ؊ exchange. In conclusion, maintenance of the bile acid pool is crucial for secretin to induce bicarbonate-rich choleresis in the normal rat and that this occurs via a chloride-bicarbonate exchange process consistent with AE2 function. (HEPATOLOGY 2006;43:266-275.) S ecretin is known to induce bicarbonate-rich hydrocholeresis in many animal species. 1-7 Its interaction with a G-protein-coupled receptor selectively localized to the epithelial bile duct cells 8 results in increased intracellular levels of cyclic adenosine monophosphate (cAMP) [cAMP] i 7,9,10 and protein kinase A activation. 11,12 Phosphorylation and opening of a cAMP-dependent Cl Ϫ channel, the cystic fibrosis transmembrane conductance regulator (CFTR), 13 causes Cl Ϫ efflux to the ductular lumen. This appears to stimulate an apical Na ϩ -independent Cl Ϫ /HCO 3 Ϫ anion exchange (AE), 14 with HCO 3 Ϫ efflux and Cl Ϫ influx, that is facilitated by the outside to inside transmembrane gradient of Cl Ϫ at relatively high intracellular HCO 3 Ϫ concentration. [10][11][12]15,16 Several bicarbonate transporters, most of them encoded by the SLC4 and SLC26 gene families, 17 have been described to exert AE activity. A decade ago, we localized one of those polypeptides, the SLC4A2 or AE2, 18 to the apical membrane in...