# Combined treatment with naringin and osthole ameliorates colitis through microbiota–amino acid metabolism and the JNK pathway

## TL;DR

Combining naringin and osthole helps treat colitis by improving gut health and reducing inflammation.

## Contribution

This study reveals the combined effects of naringin and osthole on colitis via microbiota, amino acid metabolism, and the JNK pathway.

## Key findings

- Naringin and osthole together reduce colitis symptoms more effectively than individual treatments.
- The combination downregulates the JNK/NF-κB pathway and repairs the intestinal barrier.
- Metabolomic analysis shows amino acid metabolism, especially tryptophan, is a key pathway affected.

## Abstract

Inflammatory bowel disease (IBD), particularly ulcerative colitis, involves disruption of the intestinal mucosal barrier due to ecological and metabolic imbalances in the gut as its underlying pathology. Current therapies for Ulcerative colitis (UC) exhibit limited efficacy and adverse effects, necessitating the development of novel treatment strategies. Naringin and osthole are natural herbal compounds that show therapeutic potential in various inflammatory models due to their excellent anti-inflammatory activity. However, their combined therapeutic effects and precise mechanisms in UC remain unreported. This study aimed to explore the therapeutic effectiveness and mechanism of naringin combined with osthole in addressing dextran sodium sulfate (DSS)-induced colitis. The investigation centered on their impact on the disruption of the intestinal epithelial cell barrier, modulation of intestinal flora composition, alteration of metabolites, and inflammation model in vitro. Modal assessment encompassed body weight, disease activity index (DAI) score, colon length, and histopathological examination. Intestinal barrier integrity was evaluated through Quantitative Real-Time PCR, western blotting, and immunofluorescence staining. Microbiota abundance and metabolic levels were assessed using 16S ribosomal RNA gene sequencing and metabolomics analysis. Protein expression levels of pertinent pathways and associated receptors were tested through network pharmacology prediction and western blot analysis. Naringin and osthole synergistically relieved colitis symptoms in mice compared with either drug alone or 5-aminosalicylic acid, as evidenced by weight loss recovery, DAI scores, and colon length preservation. Mechanistically, naringin combined with osthole down-regulated the expression level of JNK/NF-κB signaling pathway related proteins and repaired intestinal barrier. Furthermore, the combination regulates the composition of the microflora and promotes the restoration of a steady state of the microflora. Metabolomic revealed amino acid-tryptophan metabolism as a key metabolic pathway. It also reveals the microbiota-tryptophan pathway as a potential therapeutic strategy. Naringin combined with osthole can alleviate DSS-induced colitis more effectively by JNK/NF-κB signaling pathway, repairing barrier function and regulating intestinal microbiota and metabolites. These findings provide a theoretical basis for the combination therapy strategy to enhance the efficacy of potential functional food in treating ulcerative colitis.