A Variant of the SLC10A2 Gene Encoding the Apical Sodium-Dependent Bile Acid Transporter Is a Risk Factor for Gallstone Disease

Olga Renner,Frank Lammert,Matthias Schwab,Elke Schaeffeler,Henning Wittenburg,Stefan Winter,Simone Harsch,Marcin Krawczyk,Eduard F Stange,Jonas Rosendahl,Iris Schrijver

doi:10.1371/journal.pone.0007321

Abstract

BackgroundCholelithiasis is a multifactorial process and several mechanisms of gallstone formation have been postulated. As one of these mechanisms, a decreased expression of the ileal apical sodium-dependent bile acid transporter gene SLC10A2 in gallstone carriers was described previously. In this study the SLC10A2 gene was investigated to identify novel genetic variants and their association with gallstone formation.Methodology/Principal FindingsStudy subjects were selected with the presence or absence of gallstones confirmed by ultrasound and medical history. Genomic DNA was obtained from blood leukocytes. Sequence analysis was performed of all six exonic and flanking regions as well as of 2,400 base pairs of the SLC10A2 promoter in a cohort of gallstone carriers and control subjects from Stuttgart, Germany. Genotype frequencies of newly identified genetic variants (n = 6) and known single nucleotide polymorphisms (n = 24) were established using MALDI-TOF mass spectrometry. Six new genetic variants were found within the SLC10A2 gene. Although none of the variants was linked to gallstone disease in the Stuttgart cohort overall, the minor allele of SNP rs9514089 was more prevalent in male non-obese gallstone carriers (p = 0.06680, OR = 11.00). In a separate population from Aachen, Germany, the occurrence of rs9514089 was two-fold higher in gallstone patients (22%) than in corresponding controls (11%) (p = 0.00995, OR = 2.19). In the pooled Aachen/Stuttgart cohort rs9514089 was highly significantly linked to cholelithiasis (p = 0.00767, OR = 2.04). A more frequent occurrence was observed for male gallstone carriers (22%) compared to controls (9%) (p = 0.01017, OR = 2.99), for the total normal weight group (p = 0.00754, OR = 2.90), and for male non-obese gallstone patients (p = 0.01410, OR = 6.85). Moreover, for the minor allele of rs9514089 an association with low plasma cholesterol levels was found especially in gallstone carriers (p = 0.05).Conclusions/SignificanceWe have identified SLC10A2 as a novel susceptibility gene for cholelithiasis in humans. Comprehensive statistical analysis provides strong evidence that rs9514089 is a genetic determinant especially in male non-obese gallstone carriers. The minor allele of rs9514089 is related to differences in plasma cholesterol levels among the subjects.

Highlights

Cholelithiasis is the most common gastrointestinal disease with a prevalence of 15% in European adults [1,2,3,4]
Genetic Variations of SLC10A2 in the Stuttgart Cohort To investigate whether any of the variants were associated with gallstones, we compared the genotype frequencies of all single nucleotide polymorphisms (SNPs) in gallstone carriers and control subjects in the Stuttgart cohort
After correction by study centre, this association was only observed to display a borderline effect (p = 0.05). In this candidate gene study the SCL10A2 gene was systematically sequenced, and a first cohort from Stuttgart was genotyped for the association of a total of 30 SNPs with cholelithiasis

Summary

Introduction

Cholelithiasis is the most common gastrointestinal disease with a prevalence of 15% in European adults [1,2,3,4]. Rosmorduc et al [10] showed that rare loss of function mutations in the ABCB4 gene encoding the hepatocanalicular transporter required for biliary phospatidylcholine secretion may lead to gallstone formation in certain patients These findings in humans are consistent with the spontaneous occurrence of gallstones in Abcb knockout mice [11]. An increased gallstone risk in humans was demonstrated for the ABCG8 19H allele by a genomewide association scan with 500,000 SNPs in Caucasian individuals [12] These findings were confirmed in the combined linkage and association study by Grunhage and coworkers [13]. The results are consistent with supporting evidence from animal model that the ABCG5/G8 transporter is a lithogenic risk factor [9] Another recent association study observed an Arg64-variant of the b3-adrenergic receptor (ADRB3) more frequently in gallstone patients [14]. In this study the SLC10A2 gene was investigated to identify novel genetic variants and their association with gallstone formation

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