Multi-omics approaches and flux metabolomics for the study of familial progressive intrahepatic cholestasis type 3 (PFIC3) in cell line HepG2

Abstract

The membrane-associated protein encoded by the ABCB4 gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. Diseases associated with ABCB4 include Cholestasis, Progressive Familial Intrahepatic 3 (PFIC3), and Gallbladder Disease. Among its related pathways are regulation of lipid metabolism by Peroxisome proliferator-activated receptor alpha (PPARalpha) and Hepatic ABC Transporters. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the MDR/TAP subfamily, which are involved in multidrug resistance as well as antigen presentation. This gene encodes a full transporter and member of the p-glycoprotein family of membrane proteins with phosphatidylcholine as its substrate. The function of this protein has not yet been determined; however, it may involve the transport of phospholipids from liver hepatocytes into bile. Alternative splicing of this gene results in several products of undetermined function. Mutations in the ABCB4 gene lead to MDR3 dysfunction, which is related to the absence of biliary phospholipids resulting in decreasing transport (flow) and deficiency in the excretion of bile salts as well as in damage to the biliary epithelium and biliary canalicular, leading to cholestasis diseases. However, the molecular mechanism of MDR3 in liver cells is still poorly understood. Therefore, hepatic metabolism can be investigated using 'omics' approaches by metabolomic, lipidomic, and proteomic analysis. Moreover, metabolic flux in human hepatocytes may provide a comprehensive view of the distribution of intracellular metabolites and new insights in the characterization of intrinsic metabolic changes in the liver caused by MDR3 inactivation. The distribution of the metabolic flux is used to characterize the network topology through the stable isotope-resolved metabolomics (SIRM). In this context, hepatic metabolic models, associated metabolic, lipidomic, and proteomic studies could bring new alternatives for the treatment and diagnosis of patients with hepatic cholestasis. (AU)