Background Metabolic dysfunction-associated steatotic liver disease (MASLD) imposes a substantial global disease burden. This study aims to elucidate the role of intestinal NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome in the gut-liver axis and provide novel insights for potential therapeutic targets.

Methods Mice were fed with a methionine-choline deficient (MCD) diet for four weeks to induce MASLD models. Nlrp3 ^fl/fl and Vil1 ^cre Nlrp3 ^fl/fl mice, with a specific knockout of NLRP3 in intestinal epithelial cells, were housed either separately or together to establish models for MASLD. Liver and intestinal tissues were collected for the assessment of hepatic steatosis, inflammation, fibrosis, and integrity of the intestinal mucosal barrier, while fecal microbiota composition was analyzed using 16S rDNA sequencing. The in vivo effects of intragastric butyrate were evaluated using Vil1 ^cre Nlrp3 ^fl/fl-MCD mice.

Results Wild-type (WT)-MCD mice exhibited exacerbated hepatic steatosis and reduced intestinal NLRP3 mRNA expression compared to WT mice fed with a methionine-choline sufficient (MCS) diet, suggesting a protective role of intestinal NLRP3. The Vil1 ^cre Nlrp3 ^fl/fl-MCD vs. Nlrp3 ^fl/fl-MCD mice exhibited elevated hepatic lipid deposition and increased expression of α-SMA. Additionally, they displayed compromised intestinal mucosal barrier function characterized by shortened villi, reduced goblet cell count, and decreased expression of Reg3a and Cldn7. The co-housed Vil1 ^cre Nlrp3 ^fl/fl-MCD with Nlrp3 ^fl/fl-MCD mice showed a significantly ameliorated liver phenotype, characterized by reduced steatosis and fibrosis, in comparison with separately-housed Vil1 ^cre Nlrp3 ^fl/fl-MCD mice. This improvement was accompanied by an increased abundance of Faecalibaculum rodentium, a well-known butyrate producer. The in vivo administration of butyrate significantly ameliorated hepatic lipid accumulation and fibrogenesis in Vil1 ^cre Nlrp3 ^fl/fl-MCD mice. Further, a significant upregulation of activating protein-1 (AP-1) mRNA levels was observed in the liver of Vil1 ^cre Nlrp3 ^fl/fl-MCD mice, while both co-housed Vil1 ^cre Nlrp3 ^fl/fl-MCD mice and butyrate administration significantly exhibited downregulated expression of AP-1.

Conclusions Deletion of NLRP3 in intestinal epithelial cells leads to a reduction in the abundance of Faecalibaculum rodentium and butyrate production, resulting in the upregulation of hepatic AP-1 expression, thereby exacerbating MASLD.