TMAO promotes metabolic dysfunction-associated fatty liver disease (MAFLD) development through long-non coding RNA- highly upregulated liver cancer (HULC).

Objectives: Trimethylamine N-oxide (TMAO) is related to the pathogenesis of Metabolic dysfunction-associated fatty liver disease (NAFLD). However, the molecular mechanism of how TMAO causes MAFLD development is still unclear. The present study attempted to investigate whether TMAO contributes to MAFLD development through HULC in a cellular model of MAFLD.

Methods: HepG2 cells were cultured and induced in a fatty liver cell model. HULC knockdown was induced using the CRISPR/Cas13 system. Fatty liver cells were exposed to TMAO concentrations (75µM and 300µM) before and after HULC knockdown. RT-qPCR was used to evaluate the expression of the target genes. Apoptosis was assessed using Annexin V-FITC and PI staining. Statistical analyses included ANOVA and post-hoc tests.

Results: TMAO upregulated the expression of HULC, followed by P38MAPK overexpression (P value < 0.05). Upon HULC knockdown, TMAO could not change P3MAPK expression and its downstream targets, including TNFα, IL-6, and PNPPLA3 in fatty liver cells. Additionally, TMAO significantly induced apoptosis in the fatty acid cellular model (P value < 0.05).

Conclusion: In conclusion, the results of this study provide evidence of the TMAO/HULC/P38MAPK axis involvement in the pathogenesis of MAFLD by increasing the expression of genes involved in inflammation and fibrosis. Our data suggests that TMAO reduction could be a therapeutic target in MAFLD through gut microbiome modulation.