Non-alcoholic fatty liver disease (NAFLD) is one of the chronic liver diseases with high incidence in the world. This study aimed to investigate whether total flavonoids from Chimonanthus nitens Oliv. leaves (TFC) can ameliorate NAFLD. Herein, a high-fat diet (HFD)-induced NAFLD mice model was established, and TFC was administered orally. The results showed that TFC reduced the body weight and liver index and decreased the serum and hepatic levels of triglyceride (TG) and total cholesterol (TC). TFC significantly reduced the activity of liver functional transaminase. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) decreased by 34.61% and 39.57% in serum and 22.46% and 40.86% in the liver, respectively. TFC regulated the activities of oxidative-stress-related enzymes and upregulated the protein expression of nuclear factor E2-related factor (Nrf2)/heme oxygenase (HO-1) pathway in NAFLD mice, and the activities of total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-PX) in serum were increased by 89.76% and 141.77%, respectively. In addition, TFC reduced the levels of free fatty acids (FFA), endotoxin (ET), and related inflammatory factors in mouse liver tissue and downregulated the expression of proteins associated with inflammatory pathways. After TFC treatment, the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β in the liver tissues of NAFLD mice were downregulated by 67.10%, 66.56%, and 61.45%, respectively. Finally, TFC reduced liver fat deposition, oxidative stress, and inflammatory response to repair liver damage and alleviate NAFLD. Further studies showed that TFC regulated the expression of intestinal-barrier-related genes and improved the composition of gut microbiota. Therefore, TFC reduced liver inflammation and restored intestinal homeostasis by regulating the gut–liver axis. Overall, our findings revealed a novel function of TFC as a promising prophylactic for the treatment of NAFLD.

Chimonanthus nitens Oliv. leaves (COL), a commonly used traditional Chinese medicine, are rich in a variety of bioactive components, with flavonoids being one of the most abundant. In the current study, RAW264.7 macrophages were induced by lipopolysaccharide (LPS) and treated with COL flavonoids (COLFs). The results demonstrated that COLFs could inhibit the release of nitric oxide (NO) and related inflammatory factors in macrophages. RNA sequencing (RNA-seq) analysis revealed 627 differentially expressed genes (DEGs) in the COLF group, which were further analyzed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. We found that genes involved in biological processes in the LPS and COLF groups were significantly regulated, as indicated by the GO enrichment analysis. The NF-κB signaling pathway was identified through KEGG enrichment analysis for further exploration of the mechanism by which COLFs affect macrophages. Additionally, Western blotting analysis indicated that COLFs could influence the activity of the NF-κB/MAPK signaling pathway via the TLR4 receptor, thereby modulating its anti-inflammatory function. Overall, our results reveal a novel role for COLFs as natural inflammation regulators and provide a theoretical and molecular basis for their development and utilization.