Swertianin Suppresses M1 Macrophage Polarization and Inflammation in Metabolic Dysfunction-Associated Fatty Liver Disease via PPARG Activation

Abstract

Background: Metabolic dysfunction-associated fatty liver disease (MASLD) is closely associated with immune dysregulation and macrophage-driven inflammation. The activation of PPARG plays a critical role in modulating macrophage polarization and lipid metabolism, suggesting its potential as a therapeutic target for MASLD. Methods: We used UPLC-Q/TOF-MS and network pharmacology to investigate the key components and targets of Swertia davidi Franch, focusing on Swertianin. In vitro experiments on macrophages were conducted to assess the modulation of M1 polarization, and a mouse model of MASLD was utilized to explore the therapeutic effects of Swertianin. Results: Swertianin activated PPARG, leading to significant inhibition of M1 macrophage polarization, a reduction in lipid accumulation, and decreased inflammatory marker levels both in vitro and in vivo. The treatment significantly improved liver pathology in mice, indicating its therapeutic potential for MASLD. Conclusions: Swertianin's activation of PPARG provides a novel mechanism for treating MASLD, targeting both macrophage polarization and inflammation.

Keywords: Swertianin; inflammation; macrophage polarization; metabolic dysfunction-associated fatty liver disease; peroxisome proliferator-activated receptor-gamma.

Figure 1

Negative ion mode mass spectrometry data of Swertia davidi Franch extract. Note: Displaying mass spectrometry data of Swertia davidi Franch extract in negative ion scan mode, highlighting its high response values and detection accuracy.

Figure 2

Positive ion mode mass spectrometry data of Swertia davidi Franch extract. Note: Showing mass spectrometry data of Swertia davidi Franch extract in positive ion scan mode, emphasizing its high response values and detection quality.

Figure 3

Bioinformatics and molecular simulation analysis of the interaction between components of Swertia davidi Franch and key targets of MASLD. Note: (A) The intersection between representative components of Swertia davidi Franch in the TCSMP database and target genes related to MASLD-associated diseases; (B) Differential analysis between normal liver tissue samples (n = 60) and MASLD liver tissue samples (n = 60) in the GEO MASLD-related dataset GSE149863; (C,D) Bubble plots of GO and KEGG enrichment analysis for DEGs; (E) Intersection analysis of DEGs and target genes for the treatment of MASLD with the aforementioned compounds including Swertianin; (F) 2D and 3D structures of Swertianin from the PubChem database; (G,H) Results of molecular docking experiments demonstrating the molecular docking results using AutoDock software, especially the binding affinity of Swertianin and Rosiglitazone to PPARG and the docking results with other core targets.

Figure 4

Analysis of the effects of Swertianin on THP-1-derived macrophages. Note: (A) CCK-8 assay assessing cytotoxicity of various concentrations of PMA and Swertianin on THP-1 cells; (B) Western blot results showing the expression levels of M1 markers iNOS, TNF-α, and PPARG in macrophages after Swertianin treatment; (C) RT-qPCR results showing the expression levels of TNF-α and iNOS in Swertianin-treated macrophages; (D) Results of Oil Red O staining demonstrating the quantity and area of lipid droplets in macrophages treated with Swertianin, with a scale bar of 25 μm; (E) Biochemical analysis showing intracellular levels of TG and TC in THP-1 cells after treatment; (F) ELISA results showing the levels of TNF-α, IL-6, IL-10, and TGF-β inflammatory factors in the culture supernatant of macrophages treated with Swertianin. Data are presented as mean ± standard deviation, with cell experiments repeated three times. * p  <  0.05, ** p  <  0.01 vs. Control group; # p  <  0.05, ## p  <  0.01 vs. PMA group.

Figure 5

Analysis of the therapeutic effects of Swertianin on a MASLD mouse model. Note: (A) Experimental flowchart illustrating the overall experimental procedure of establishing a MASLD mouse model and treating it with Swertianin; (B) Biochemical analysis results showing changes in serum TG and TC levels in mice after treatment; (C) ELISA detection results showing changes in serum levels of inflammatory factors (such as TNF-α and IL-6); (D) Evaluation of M1 polarization marker CD86, iNOS, and TNF-αusing flow cytometry; (E) Pathological analysis results of liver tissue showing H&E-stained liver tissue sections, with a scale bar of 50 μm; (F) Oil Red O staining to assess lipid accumulation levels, with a scale bar of 50 μm; (G) NAS scoring of liver histopathology; (H,I) Analysis of M1 macrophage markers and PPARG expression in liver tissue demonstrating Western blot and RT-qPCR results; (J) PPARG expression in liver tissue. * p  <  0.05, ** p  <  0.01 vs. Control group; # p  <  0.05 vs. Model group. Data are presented as mean ± standard deviation, n = 10.