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Filter by:Rationale: Bile salts are potent signalling molecules influencing various metabolic and functional processes. Bile salts exert these functions by activating nuclear (e.g. FXR ) and plasma cell membrane-bound receptors (e.g. TGR5) which are expressed in several tissues (e.g. liver, small intestine, colon, kidney and gallbladder). Bile salts regulate their own biosynthesis by controlling the transcription of the hepatic bile salt synthetic enzyme CYP7A1. Two pathways are involved in the negative feedback control of bile salt synthesis: i) the hepatic FXR-SHP pathway and ii) the ileal FXR-FGF19 pathway. Studies showed that the latter is more prominent in controlling CYP7A1 transcript levels (viz. bile salt synthesis). Thus, bile salts are synthesized in the liver, excreted in bile and expelled by the gallbladder into the proximal intestine (to aid in lipid absorption and digestion) and reabsorbed in the terminal ileum to recycle back to the liver via portal blood. Bile salts reclaimed from the intestinal lumen by the ileocyte, activate FXR. This induces the expression of an enterokine, FGF19, which signals via portal blood to the liver to activate its receptor which initiates downstream signalling to repress bile salt synthesis. The FXR/FGF19 signalling pathway is the subject of the present study. Patients with obstructive cholestasis (=accumulation of bile) caused by malignancies (e.g. pancreatic cancer, cholangiocarcinoma) have a perturbed enterohepatic cycle. Obstructive cholestasis is associated with i) gut barrier dysfunction, ii) endotoxemia, iii) bacterial overgrowth and iv) liver injury. Previous study showed that FGF19 is expressed in the liver of patients with obstructive cholestasis. However, knowledge about the contribution of FGF19 protein by the gut in obstructive cholestasis has thus far been unexplored. Preliminary findings revealed that FGF19 is produced by the portal drained viscera (viz. intestine) of non-cholestatic patients undergoing liver surgery. The inter-organ signalling of FGF19 in an obstructed entero-hepatic cycle has not yet been characterized and likewise the metabolic and other functional effects of inflicted FGF19 signalling during cholestasis have not been clarified. The hypothesis is that the FXR-FGF19 pathway is disturbed in patients with obstructive cholestasis, and this is associated with organ injury and metabolic dysfunction. The investigators postulate that FGF19 is not produced by the terminal ileum under conditions of obstructive cholestatic, but production is shifted to the liver and this affects metabolic processes. The aim of this study is to investigate FGF19 signalling in patients with cholestasis compared to non-cholestatic patients or post-cholestatic patients (drained patients) by calculating fluxes across the portal drained organs. Secondly, the investigators aim to investigate the metabolic and functional consequences (glucose, lipid homeostasis, cholestatic itch, gut barrier function) of a disturbed FXR-FGF19 pathway in humans. This study will provide insights that may lead to potential therapeutic strategies for patients with a disturbed enterohepatic cycle (e.g. cholestatic liver diseases). Study population: Adult (>18 years old) cholestatic (cholestasis group), drained (restored enterohepatic cycle) and non-cholestatic patients (controls, normal enterohepatic circulation) undergoing pancreaticoduodenectomy (Whipple procedure) for hepatopancreaticobiliary malignancies (e.g. pancreatic cancer, cholangiocarcinoma) or liver resection for hepatic malignancies (e.g. cholangiocarcinoma, colorectal liver metastases) are eligible for this study. Study period: inclusion is planned from 1.12.2017 until 1.12.2024
The expression of transporters involved in bile acid homeostasis is differentially regulated during obstructive cholestasis. Bile acids are also substrates of the drug efflux transporter breast cancer resistance protein (BCRP) that is highly expressed in the human intestine. Therefore we intend to analyze whether intestinal BCRP expression could be altered during cholestasis.