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Title: Critical illness evokes elevated circulating bile acids related to altered hepatic transporter and nuclear receptor expression
Authors: Vanwijngaerden, Yoo-Mee *
Wauters, Joost *
Langouche, Lies
Vander Perre, Sarah
Liddle, Christopher
Coulter, Sally
Vanderborght, Sara
Roskams, Tania
Wilmer, Alexander
Van den Berghe, Greet
Mesotten, Dieter # ×
Issue Date: Nov-2011
Publisher: W.B. Saunders
Series Title: Hepatology vol:54 issue:5 pages:1741-1752
Article number: 10.1002/hep.24582
Abstract: Hyperbilirubinemia is common during critical illness and is associated with adverse outcome. Whether hyperbilirubinemia reflects intensive care unit (ICU) cholestasis is unclear. Therefore, the aim of this study was to analyze hyperbilirubinemia in conjunction with serum bile acids (BAs) and the key steps in BA synthesis, transport, and regulation by nuclear receptors (NRs). Serum BA and bilirubin levels were determined in 130 ICU and 20 control patients. In liver biopsies messenger RNA (mRNA) expression of BA synthesis enzymes, BA transporters, and NRs was assessed. In a subset (40 ICU / 10 controls) immunohistochemical staining of the transporters and receptors together with a histological evaluation of cholestasis was performed. BA levels were much more elevated than bilirubin in ICU patients. Conjugated cholic acid (CA) and chenodeoxycholic acid (CDCA) were elevated, with an increased CA/CDCA ratio. Unconjugated BA did not differ between controls and patients. Despite elevated serum BA levels, CYP7A1 protein, the rate-limiting enzyme in BA synthesis, was not lowered in ICU patients. Also, protein expression of the apical bile salt export pump (BSEP) was decreased, whereas multidrug resistance-associated protein (MRP) 3 was strongly increased at the basolateral side. This reversal of BA transport toward the sinusoidal blood compartment is in line with the increased serum conjugated BA levels. Immunostaining showed marked down-regulation of nuclear farnesoid X receptor, retinoid X receptor alpha, constitutive androstane receptor, and pregnane X receptor nuclear protein levels. Conclusion: Failure to inhibit BA synthesis, up-regulate canalicular BA export, and localize pivotal NR in the hepatocytic nuclei may indicate dysfunctional feedback regulation by increased BA levels. Alternatively, critical illness may result in maintained BA synthesis (CYP7A1), reversal of normal BA transport (BSEP/MRP3), and inhibition of the BA sensor (FXR/RXRα) to increase serum BA levels. (HEPATOLOGY 2011;).
URI: 
ISSN: 0270-9139
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Laboratory for Intensive Care Medicine (-)
Department of Experimental Medicine (-)
Translational Cell & Tissue Research
Laboratory for Clinical Infectious and Inflammatory Disorders
Laboratory of Intensive Care Medicine
* (joint) first author
× corresponding author
# (joint) last author

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