Gastroenterology

Gastroenterology

Volume 117, Issue 6, December 1999, Pages 1370-1379
Gastroenterology

Liver, Pancreas, and Biliary Tract
Hepatocanalicular bile salt export pump deficiency in patients with progressive familial intrahepatic cholestasis,☆☆

https://doi.org/10.1016/S0016-5085(99)70287-8Get rights and content

Abstract

Background & Aims: Progressive familial intrahepatic cholestasis (PFIC), an inherited liver disease of childhood, is characterized by cholestasis and either normal or increased serum γ-glutamyltransferase activity. Patients with normal γ-glutamyltransferase activity have mutations of the FIC1 locus on chromosome 18q21 or mutations of the BSEP gene on chromosome 2q24. Also, patients with bile acid synthesis defects have low γ-glutamyltransferase activity. We investigated expression of the bile salt export pump (BSEP) in liver samples from patients with a PFIC phenotype and correlated this with BSEP gene mutations.

Methods: BSEP and multidrug resistance protein 2 (MRP2) expressions were studied by immunohistochemistry in liver specimens of 28 patients and BSEP gene mutation analysis in 19 patients. Bile salt kinetics were studied in 1 patient.

Results: Sixteen of 28 liver samples showed no canalicular BSEP staining. Staining for MRP2 showed a normal canalicular pattern in all but 1 of these samples. Ten of 19 patients showed BSEP gene mutations; BSEP protein expression was lacking in all 10 patients. No mutations were found in 9 of 19 patients, and in all except 1, BSEP protein expression was normal. Bile salt concentration in bile of BSEP-negative/MRP2-positive PFIC patients was 0.2 ± 0.2 mmol/L (n = 9; <1% of normal) and in BSEP-positive PFIC patients 18.1 ± 9.9 mmol/L (n = 3; 40% of normal). The kinetic study confirmed the dramatic decrease of bile salt secretion in BSEP-negative patients.

Conclusions: The findings show a close correlation between BSEP gene mutations and canalicular BSEP expression. Biliary secretion of bile salts is greatly reduced in BSEP-negative patients.

GASTROENTEROLOGY 1999;117:1370-1379

Section snippets

Patients from the Groningen center

Patient A is a female born to nonconsanguineous parents who presented with neonatal cholestasis. In the first year of life, the serum alkaline phosphatase (ALP) activity was 393 U/L (normal [N] < 220 U/L), GGT 27 U/L (N < 45 U/L), total bilirubin 83 μmol/L (N < 17 μmol/L), conjugated bilirubin 54 μmol/L (N < 5 μmol/L), and serum bile salts 530 μmol/L (N < 9 μmol/L). The patient has 1 affected and 1 nonaffected sibling. At the age of 5 years, her serum bilirubin value was 48 μmol/L, conjugated

Characterization of BSEP antibodies

The rabbit polyclonal BSEP antibody detects a 170-kilodalton protein band in Western blots from canalicular enriched subfractions prepared from human, mouse, and rat liver (Figure 1).

. Western blot analysis of BSEP in canalicular subfractions from humans, mice, and rats using rabbit immunoglobulin G anti-BSEP antibodies. Samples from liver subfractions enriched in canalicular membranes were subjected to Western blot analysis.

The molecular mass of BSEP has been reported to be 170 kilodaltons.14,

Discussion

PFIC is a heterogeneous group of diseases with various clinical manifestations and causes, including defects of hepatocanalicular transport of bile salts or phospholipids and defects of bile acid synthesis. Bile acid synthesis defects seem to be rare. The frequency of transport defects is not known, but this study shows that the combined cohorts of 3 liver transplantation centers yielded 28 patients with a PFIC phenotype with predominantly low serum GGT activity.

Liver samples from 16 of 28

Acknowledgements

The authors thank Micheline Dumont (INSERM, Hôpital Beaujon, Paris, France) for the bile salt analysis of the patients at Hôpital de Bicêtre, Paris, France; Gerard Dijkstra for his help with the photography; and Renze Boverhof (University Hospital Groningen) for the bile salt analysis of the patients in Groningen.

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    Address requests for reprints to: Peter L. M. Jansen, M.D., Division of Hepatology and Gastroenterology, University Hospital Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands. e-mail: [email protected]; fax: (31) 50-3619306.

    ☆☆

    Supported by the Netherlands Organization for Scientific Research, NWO Program 902-23-191. E.J. and M.H. were supported by the Association Française contre les Myopathies, and the Assistance Publique-Hôpitaux de Paris (CRC no. 97001), Paris, France. R.J.T. is a Wellcome Advanced Fellow; S.S.S. is supported by grants from the Medical Research Council and the Children's Liver Disease Foundation.

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