Alistipes putredinis Ameliorates Metabolic Dysfunction-Associated Steatotic Liver Disease in Rats via Gut Microbiota Remodeling and Inflammatory Suppression

Abstract

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a highly prevalent chronic liver condition linked to obesity and metabolic imbalance. Alterations in the gut microbiota are increasingly recognized as contributors to its progression. Alistipes putredinis, a core member of the human gut microbiota, has been linked with metabolic health, but its functional role in MASLD remains unclear. Methods: This study evaluated the potential of A. putredinis strain Ap77, isolated from the stool of a healthy adult, to mitigate MASLD-related alterations in a high-fat diet (HFD)-induced rat model. Animals were divided into normal chow (NC), HFD, and HFD plus Ap77 groups and received daily oral gavage of Ap77 or PBS for 8 weeks. Results: Ap77 supplementation attenuated the body weight increase associated with high-fat diet consumption. It also reduced hepatic triglyceride levels and fat mass and improved liver histology. Transcriptomic analysis revealed suppression of inflammation-associated pathways. Correspondingly, the concentrations of IL-1β, IL-6, and TNF-α in both the liver and serum were reduced. Ap77 supplementation was associated with an increased abundance of health-associated bacterial genera, such as Lachnospiraceae UCG_010, Akkermansia, and Flavonifractor, as well as elevated serum levels of butyrate, indole-3-propionic acid, and indoleacrylic acid. Notably, correlation analysis revealed that Lachnospiraceae UCG_010 was positively associated with these metabolites. Conclusions:A. putredinis Ap77 alleviates hepatic steatosis and inflammation in MASLD, potentially by reshaping gut microbiota and suppressing inflammation-related signaling pathways.

Keywords: Alistipes putredinis; MASLD; butyrate; gut microbiota; indole derivatives; inflammation.

Figure 1

Ap77 administration alters weight gain, consumption, and tissue mass. (A) Overview of the experimental setup. (B) Weekly changes in body weight. (C) Total body weight gain. (D) Liver weight. (E) Liver coefficient. (F) Epididymal fat weight. (G) Caloric intake. (H) Food efficiency ratio (FER). Data are presented as mean ± SD (n = 8 per group). * p < 0.05; ** p < 0.01; *** p < 0.001; ns, not significant.

Figure 2

Effects of Ap77 on liver function in MASLD rats. (A) Serum ALT levels. (B) Serum AST levels. (C) Serum ALP levels. (D) H&E staining of liver sections; black arrows indicate steatosis and blue arrows indicate ballooning (scale bar, 50 μm). (E) NAS. (F) Hepatic TG content. Data are presented as mean ± SD (n = 8 per group). * p < 0.05, *** p < 0.001.

Figure 3

Serum lipid regulation and adipose morphology by Ap77. (A) Serum TC levels. (B) Serum TG levels. (C) Serum LDL-C levels. (D) Serum HDL-C levels. (E) Serum FFA levels. (F) H&E-stained sections of epididymal adipose tissue; scale = 100 μm. (G) Adipocyte number. Data are presented as mean ± SD (n = 8 per group). * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 4

Transcriptomic analysis of liver tissues. (A) Volcano plot of the DEGs’ distribution. DEGs: red = upregulated; blue = downregulated. (B) Venn diagram showing overlapping DEGs across groups. (C) Bubble plot of KEGG-enriched pathways for DEGs shared among the three groups. Red boxes indicate inflammation-related pathways identified by KEGG analysis. (D–G) GSEA results for inflammation-related pathways. The green curve represents the enrichment score (ES); red indicates upregulated genes and blue indicates downregulated genes.

Figure 5

Changes in hepatic and serum cytokines following Ap77 administration. (A–C) Hepatic levels of TNF-α, IL-1β, and IL-6. (D–F) Circulating concentrations of TNF-α, IL-1β, and IL-6 in serum. Data are presented as mean ± SD (n = 8 per group). * p < 0.05, *** p < 0.001.

Figure 6

Effects of Ap77 on gut microbiota. (A) α-diversity assessed by ACE and Chao1 indices. (B) β-diversity visualized by PCoA. (C) Genus-level composition of fecal microbiota. (D) Differentially abundant genera identified by LEfSe analysis. Data are presented as mean ± SD (n = 8 per group). * p < 0.05; ** p < 0.01.

Figure 7

Serum metabolite alterations induced by Ap77 in MASLD rats. (A) Volcano plot of HFD vs. Ap77 metabolites. The dashed lines indicate the thresholds for log2 fold change and p-value. (B,C) Serum IPA and IA levels. (D) Radar chart of average SCFA profiles. (E) Serum butyrate levels. (F) Spearman correlation between key genera and metabolites. Colors denote correlation direction: red for positive and blue for negative. Asterisks denote significant correlations. Data are presented as mean ± SD (n = 4 per group). * p < 0.05; ** p < 0.01; *** p < 0.001; ns, not significant.

Figure 8

Mechanisms by A. putredinis Ap77 alleviates MASLD in HFD-fed rats. A. putredinis Ap77 improves lipid metabolism, reshapes the gut microbiota, promotes the production of beneficial microbial metabolites (IPA, IA, butyrate), and reduces hepatic inflammation.