Long-term subcutaneous injection of lipopolysaccharides and high-fat diet induced non-alcoholic fatty liver disease through IKKε/ NF-κB signaling

Abstract

Non-alcoholic fatty liver disease (NAFLD) was associated with increased level of lipopolysaccharides (LPS) which mechanism remained unclear on intervention between LPS and NAFLD. The aim was to explore the IKKε/NF-κB role and its intervention of LPS and high-fat diet (HFD) induced NAFLD. Male C57BL/6 mice were fed on high-fat diet (HFD) combined with or without simultaneously subcutaneous injection of LPS for 18 weeks. Body weight , blood biochemistry parameters, inflammatory mediator and liver lipid deposition were measured to evaluate LPS effect on NAFLD. Furthermore, IKKε selective inhibitor amlexanox (AM) was administrated by gavage to HFD + LPS induced mice. The indicators about metabolism and inflammation were examined and qRT-PCR, immunoblotting assay as well as immunohistochemistry were performed to assess IKKε/NF-κB activation and downstream gene expression. This study found that low-dose LPS + HFD aggravated more significant steatosis than simple HFD or high-dose LPS + HFD. Low-dose LPS exacerbated more prominent inflammation profile including increased IKKε and NF-κB expression in liver than HFD. Inhibiting IKKε/NF-κB signaling with amlexanox significantly prevented HFD + LPS induced metabolic disorders and hepatic steatosis. LPS-upregulated gene expression involved in glucolipid metabolism could be downregulated by amlexanox. Thus, the present study confirmed long-term combinational administration of subcutaneous low-dose LPS injection and HFD induced NAFLD model which had more significant phenotype in mice than simple HFD or high-dose LPS-induction. Targeting on IKKε/NF-κB signaling with its inhibitor amlexanox alleviated steatohepatitis, suggesting that IKKε/NF-κB signaling was responsible for effect of LPS and HFD on NAFLD.