Hepatitis C virus (HCV) is a hepatotrophic virus and a major cause of chronic liver disease, including hepatocellular carcinoma, worldwide. The life cycle of HCV is closely associated with the metabolism of lipids and lipoproteins. The main function of lipoproteins is transporting lipids throughout the body. Triglycerides, free cholesterol, cholesteryl esters, and phospholipids are the major components of the transported lipids. The pathway of HCV assembly and secretion is closely linked to lipoprotein production and secretion, and the infectivity of HCV particles largely depends on the interaction of lipoproteins. Moreover, HCV entry into hepatocytes is strongly influenced by lipoproteins. The key lipoprotein molecules mediating these interactions are apolipoproteins. Apolipoproteins are amphipathic proteins on the surface of a lipoprotein particle, which help stabilize lipoprotein structure. They perform a key role in lipoprotein metabolism by serving as receptor ligands, enzyme co-factors, and lipid transport carriers. Understanding the association between the life cycle of HCV and lipoprotein metabolism is important because each step of the life cycle of HCV that is associated with lipoprotein metabolism is a potential target for anti-HCV therapy. In this article, we first concisely review the nature of lipoprotein and its metabolism to better understand the complicated interaction of HCV with lipoprotein. Then, we review the outline of the processes of HCV assembly, secretion, and entry into hepatocytes, focusing on the association with lipoproteins. Finally, we discuss the clinical aspects of disturbed lipid/lipoprotein metabolism and the significance of dyslipoproteinemia in chronic HCV infection with regard to abnormal apolipoproteins.
Background & Aims: The incidence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. We evaluated serum collagen IV as a direct non-invasive marker of severe liver fibrosis in NAFLD.Methods: The study included 148 NAFLD and 187 chronic hepatitis C patients in whom histological severity of liver fibrosis was evaluated. The utility of serum collagen IV measured by immune-mediated agglutination using two types of monoclonal antibodies for distinguishing severe fibrosis (≥ stage 3 and ≥ F3) from non-to-moderate fibrosis in NAFLD or chronic hepatitis C was assessed in comparison to serum hyaluronic acid or other indirect fibrosis markers.Results: Multiple logistic regression analysis showed that serum collagen IV was significantly associated with severe fibrosis in NAFLD (odds ratio: 1.21, p<0.001) but not in chronic hepatitis C. For distinguishing severe fibrosis in NAFLD, collagen IV showed the largest area under the receiver-operating characteristic curve (0.827, 95%CI: 0.746-0.908) followed by FIB-4 (0.805, 95%CI: 0.728-0.890); in chronic hepatitis C, those for FIB-4 (0.813, 95%CI: 0.748-0.878) and collagen IV (0.770, 95%CI: 0.683-0.857) were the largest and smallest, respectively. To detect severe fibrosis in NAFLD, a cutoff of collagen IV > 177 exhibited 77.1% sensitivity, 84.0% specificity, 76.5% positive predictive value, and 84.0% negative predictive value. Combined with a cutoff of FIB-4 > 2.09, the negative and positive predictive values, and specificity for detecting severe fibrosis in NAFLD increased further.Conclusion: Collagen IV is a reliable marker for distinguishing severe liver fibrosis from non-to-moderate fibrosis in NAFLD but not chronic hepatitis C.
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