CLINICAL SIGNIFICANCE OF SERUM EXOSOMAL miRNA IN LIVER FIBROGENESIS OF NON-ALCOHOLIC FATTY LIVER DISEASE

초록

Background: Fatty liver disease in non-significant amount of alcoholic drinker (Non-alcoholic fatty liver disease (NAFLD)) is on the rise worldwide as obesity and diabetes increase. Among histologic changes, the degree of liver fibrosis is the most important factor for predicting long term outcomes. Although liver biopsy is the gold standard for diagnosis, it is difficult to be done in routine clinical practice due to the risk of serious complications and variabilities of sampling and interpretation. The aim of this study was to explore clinical significance of serum exosomal miRNA in liver fibrogenesis of NAFLD patients. Methods: A total of 41 biopsy-proven NAFLD patients were included. Exosomes were isolated from serum samples and exosomal miRNAs were analyzed with GeneChip miRNA 4.0 array (Affymetrix, U.S.A). Expression levels of miRNAs in liver tissues of the same patient who had been tested for serum exosomal miRNA were analyzed. To define the role of miRNA in liver fibrogenesis, hepatocytes or stellate cells were transfected with miRNA of interest. Results: NAFLD patients with significant fibrosis (Group 1) were older than those with non-significant fibrosis (Group 2). The percentage of patients who had metabolic syndrome was higher in Group 1. In addition, Group 1 patients had lower platelet counts and prolonged PT INR. A total of 86 serum exosomal miRNAs showed significant differences in expression between the two groups. Of these, 42 miRNAs showed significantly higher expression while 44 miRNAs showed significantly lower expression in Group 1 than in Group 2. MiR4668-5p, 3613-3p, 8075, 619-5p, 1184 showed higher expression levels in Group 1 than in Group 2. When human stellate cells (LX2 cells) were transfected with miR4668-5p inhibitors or miR4668-5p mimics, TGF-b, collagen1A1, and a-SMA mRNA expression levels were significantly decreased by miR 4668-5p inhibitors. However, their expression levels or significantly increased after transfections with miR4668-5p mimics. Conclusion: Serum exosomal miRNAs showed significantly altered expression in NAFLD patients with significant fibrosis. Although additional researches are required, serum exosomal miRNA might have a diagnostic value for advanced fibrosis or serve as therapeutic targets for liver fibrogenesis in NAFLD patients.