A total of 32 male SD rats were randomly divided into control group， model group， negative control group （mimic-NC group），and miR-490-3p mimic group （miR-490-3p mimic group），and there were 8 rats in each group. The rats were fed with high-fat diet to replicate the NAFLD rat models. The rats in control group were given nothing，and the rats in mimic-NC and miR-490-3p mimic groups were injected with adenovirus containing meaningless sequence and miR-490-3p mimic plasmid through tail vein， respectively. The expression levels of miR-490-3p in liver tissue of the rats in various groups were detected by Real-time fluorescence quantitative （RT-qPCR）method. The serum levels of alanine aminotransferase （ALT），aspartate aminotransferase （AST）， tumor necrosis factor-α （TNF-α）， interleukin-6 （IL-6）， interleukin-1β （IL-1β）， malondialdehyde （MDA）， superoxide dismutase （SOD）， glutathione peroxidase （GSH-Px） in liver tissue of the rats in various groups were detected by ELASA method. The pathomorphology of liver tissue of the rats in various groups were detected by HE staining and Oil red O staining.The expression levels of Toll-like receptor 4 （TLR4） and nuclear factor κB （NF-κB） mRNA in liver tissue of the rats in various groups were detected by RT-qPCR method.The expression levels of TLR4 and NF-κB proteins in liver tissue of the rats in various groups were detected by Western blotting method.

Compared with control group， the serum levels of ALT， AST， TNF-α， IL-6， IL-1β and MDA， the expression levels of TLR4 mRNA and protein and NF-κB mRNA in liver tissue of the rats in model group were increased（P<0.05）；while the serum levels of SOD and GSH-Px and expression level of miR-490-3p in liver tissue were decreased （P<0.05）. Compared with model group， the serum levels of ALT， AST， TNF-α， IL-6， IL-1β， and MDA and the expression levels of TLR4 mRNA and protein and NF-κB mRNA in liver tissue of the rats in miR-490-3p mimic group were decreased（P<0.05）， while the levels of serum SOD and GSH-Px， and the expression level of miR-490-3p in liver tissue were increased （P<0.05）.The HE staining results showed that the hepatocytes of the rats in control group were evenly arranged， a large amount of fat was accumulated in the hepatocytes in model group and mimic-NC group， and there was obvious inflammatory cell infiltration in the portal area， and some hepatocytes were necrotic and fibrotic； the degree of liver lesions in miR-490-3p mimic group was less than that in model group. The oil red O staining results showed that there were no obviously red stained fat droplets in liver tissue of the rats in control group，and the obviously red stained fat droplets were found in liver tissue of the rats in model group and mimic-NC group， with large quantity and volume； the volume and quantity of fat droplets in liver tissue of the rats in miR-490-3p mimic group were significantly reduced.

Over-expression of miR-490-3p can relieve the NAFLD damage，and its mechanism may be related to blocking the TLR4/NF-κB signaling pathways， reducing the inflammation response，and improving the oxidative stress.