A common variant in the hepatobiliary phospholipid transporter ABCB4 modulates liver injury in PBC but not in PSC : prospective analysis in 867 patients

Background: The ATP-binding cassette subfamily B member 4 (ABCB4) gene encodes the hepatic phospholipid transporter. Variants in the ABCB4 gene are associated with various cholestatic phenotypes, some of which progress to liver fbrosis and cirrhosis. The aim of our study was to investigate the role of the cholestasis-associated variant ABCB4 c.711A>T (p.I237I, rs2109505) in patients with primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Results: Two cohorts of Polish patients took part in this study. The Szczecin cohort comprised 196 patients with PBC (174 females, 38% with cirrhosis) and 135 patients with PSC (39 females, 39% with cirrhosis). The Warsaw cohort consisted of 260 patients with PBC (241 females, 44% with cirrhosis) and 276 patients with PSC (97 females, 33% with cirrhosis). Two control cohorts—150 healthy blood donors and 318 patients without liver disease, were recruited in Szczecin and in Warsaw, respectively. The ABCB4 c.711A>T polymorphism was genotyped using TaqMan assay. In both PBC cohorts, carriers of the risk variant presented more frequently with cirrhosis (Szczecin: OR=1.841, P=0.025; Warsaw: OR=1.528, P=0.039). The risk allele was associated with increased serum AST, GGT and ALP (all P<0.05) at inclusion. During the follow-up, patients in both cohorts signifcantly improved their laboratory results, independently of their ABCB4 c.711A>T genotype (P>0.05). During 8±4 years follow-up, a total of 22 patients in the Szczecin PBC group developed cirrhosis, and this risk was higher among carriers of the risk variant (OR=5.65, P=0.04). In contrast to PBC, we did not detect any association of ABCB4 c.711A>T with a liver phenotype in PSC cohorts. Conclusions: The frequent pro-cholestatic variant ABCB4 c.711A>T modulates liver injury in PBC, but not in PSC. In particular, carriers of the major allele are at increased risk of progressive liver scarring