Case Report
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World J Gastroenterol. Dec 21, 2006; 12(47): 7710-7714
Published online Dec 21, 2006. doi: 10.3748/wjg.v12.i47.7710
Analysis of ileal sodium/bile acid cotransporter and related nuclear receptor genes in a family with multiple cases of idiopathic bile acid malabsorption
Marco Montagnani, Anna Abrahamsson, Cecilia Gälman, Gösta Eggertsen, Hanns-Ulrich Marschall, Elisa Ravaioli, Curt Einarsson, Paul A Dawson
Marco Montagnani, Elisa Ravaioli, Dipartimento di Medicina Interna e Gastroenterologia, Università di Bologna, Bologna, Italy
Marco Montagnani, Elisa Ravaioli, Center for Applied Biomedi-cal Research, Università di Bologna, Bologna, Italy
Anna Abrahamsson, Hanns-Ulrich Marschall, Curt Einarsson, Center for Gastroenterology and Hepatology, Karolinska University Hospital Huddinge, Stockholm, Sweden
Cecilia Gälman, Center for Metabolism and Endocrinology, Karolinska University Hospital Huddinge, Stockholm, Sweden
Gösta Eggertsen, Department of Laboratory Medicine, Division of Clinical Chemistry, Karolinska University Hospital Huddinge, Stockholm, Sweden
Paul A Dawson, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27157, United States
Author contributions: All authors contributed equally to the work.
Supported by grants from the Swedish Research Council, the Karolinska Institutet and the Swedish Society of Medicine (to CE) and National Institutes of Health grants DK-47987 (to PAD)
Correspondence to: Paul A Dawson, PhD, Department of Internal Medicine, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, United States. pdawson@wfubmc.edu
Telephone: +1-336-7164633 Fax: +1-336-7166279
Received: September 19, 2006
Revised: November 12, 2006
Accepted: November 20, 2006
Published online: December 21, 2006
Abstract

The etiology of most cases of idiopathic bile acid malabsorption (IBAM) is unknown. In this study, a Swedish family with bile acid malabsorption in three consecutive generations was screened for mutations in the ileal apical sodium-bile acid cotransporter gene (ASBT; gene symbol, SLC10A2) and in the genes for several of the nuclear receptors known to be important for ASBT expression: the farnesoid X receptor (FXR) and peroxisome proliferator activated receptor alpha (PPARα). The patients presented with a clinical history of idiopathic chronic watery diarrhea, which was responsive to cholestyramine treatment and consistent with IBAM. Bile acid absorption was determined using 75Se-homocholic acid taurine (SeHCAT); bile acid synthesis was estimated by measuring the plasma levels of 7α-hydroxy-4-cholesten-3-one (C4). The ASBT, FXR, and PPARα genes in the affected and unaffected family members were analyzed using single stranded conformation polymorphism (SSCP), denaturing HPLC, and direct sequencing. No ASBT mutations were identified and the ASBT gene did not segregate with the bile acid malabsorption phenotype. Similarly, no mutations or polymorphisms were identified in the FXR or PPARα genes associated with the bile acid malabsorption phenotype. These studies indicate that the intestinal bile acid malabsorption in these patients cannot be attributed to defects in ASBT. In the absence of apparent ileal disease, alternative explanations such as accelerated transit through the small intestine may be responsible for the IBAM.

Keywords: Bile acid malabsorption; Diarrhea; Genetics; 75Se-homocholic acid taurine test; Nuclear receptors