Genetic variant c.711A>T in the hepatobiliary phospholipid transporter ABCB4 is associated with significant liver fibrosis.

Abstract

Liver fibrosis is the common consequence of chronic liver diseases (CLD). Recently liver stiffness measurements (LSM) ≥ 9.1 kPa, as determined by transient elastography (TE), were demonstrated to predict significant fibrosis (stages ≥ F2) in a population-based setting. The PNPLA3 (adiponutrin) p.I148M polymorphism enhances the risk of liver injury. The aim of our study was to investigate the association between the procholestatic ABCB4 polymorphism c.711A>T and LSM ≥ 9.1 kPa in humans as well as the interaction between ABCB4 and PNPLA3 in a mouse model of chronic cholestasis. Prospectively, we recruited 712 patients with CLD (278 women, age 50 ± 13 years) with available TE results; liver biopsy results were available in 165 individuals. The ABCB4 c.711 genotype was determined by PCR-based assays. PNPLA3 expression and liver injury were studied in Abcb4-/- mice and wild-type controls. Overall, median LSM in our cohort was 6.7 kPa, and 226 individuals had LSM ≥ 9.1 kPa. Carriers of the ABCB4 variant c.711A presented more frequently with LSM ≥ 9.1 kPa (OR = 1.33, P = 0.020) and FIB-4 score ≥ 2.67 (OR = 1.38, P = 0.040). The presence of the risk allele was associated (P = 0.002) with FIB-4. In a multivariate model, the ABCB4 variant (OR = 1.43, P = 0.047) as well as BMI (P = 0.043, OR = 1.04) and age (OR = 1.02, P < 0.010) were independent risk factors for fibrosis stage ≥ F2. Abcb4 deficiency in mice led to enhanced liver injury, coupled with a decrease (P = 0.020) of hepatic PNPLA3 expression. To conclude, the procholestatic variant ABCB4 c.711A>T might represent a new genetic risk factor for clinically significant liver fibrosis. Lower expression of PNPLA3 in fibrotic Abcb4-/- livers points to the interaction between phospholipid metabolism and PNPLA3 in progressive liver injury.