P051 Molecular and bioinformatics analysis of miR29b in steatosis

The liver is the largest solid organ in human, which detoxifies various chemicals, metabolises nutrients and supports almost every organ in the body. Thus, the liver is prone to many diseases. Non-alcoholic fatty liver disease (NAFLD) is characterised by excessive lipid accumulation in the liver, progressing to severe liver diseases, including fibrosis and cirrhosis. MicroRNAs (miRNAs), the small and non-coding RNAs, are involved in various biological processes by regulating gene expression at transcriptional or translational levels. MiR29b has been regarded as a potential antifibrotic agent through targeting several pathological processes. However, the mechanistic role of miR29b in the development of NAFLD remains unclear. The aim of this study examined the role of miR29b in NAFLD progression through a combination of molecular and bioinformatics approaches. MiR29b mimics were transfected into mice hepatocytes. RNA was isolated from hepatocytes overexpressing miR29b. RNA-seq and Gene Set Enrichment Analysis (GSEA) were utilised to identify the significant biological pathway regulated by miR29b. Mice were injected with streptozotocin (STZ) and then fed with a high-fat diet for 6, 8 and 12 weeks to induce simple steatosis, NASH and fibrosis, which represent the different stages of NAFLD. Liver tissues from these mice were collected for histological analysis and gene or protein level detection by q-RT-PCR and Western blotting. The target genes of miR29b were predicted using the prediction tool-Targetscan and verified using luciferase assays. Mice were treated with polymeric micelles carrying miR29b to determine its therapeutic effect in the progression of NAFLD. Using RNA-seq, we uncovered 1,115 mRNAs and 73 lncRNAs were significantly deregulated (q≤0.1) owing to miR29b overexpression. The lipid metabolism-related pathways were predominately upregulated by miR29b (figure 1). Systems-level analysis revealed that miR-29b levels were significantly decreased during the pathogenetic stages from liver steatosis to fibrosis. The reduced levels of miRNA29b were associated with lipid accumulation and inflammation in the liver. Further investigation revealed that miR29b degraded Insulin Receptor Substrate 1(IRS1) via directly targeting its 3’UTR. Moreover, mice injected with miR29b micelles alleviated hepatic lipid accumulation via downregulating fatty acid synthesis through IRS1-related pathway and enhanced β-oxidation. We report that lipid metabolism-related pathways were significantly upregulated by miR29b. MiR29b ameliorated hepatic lipid accumulation via directly targeting IRS1-regulated lipid metabolism. In addition, the analysis of other impacted biological pathways and the networks involving miR29b and hepatic-associated mRNAs or non-coding RNAs is in progress.