# Dietary hydrolysable tannin improves intestinal health of largemouth bass (Micropterus salmoides): insights from NF-κB signaling pathway and arachidonic acid metabolism

## TL;DR

This study shows that adding hydrolysable tannin to fish feed can improve intestinal health and growth in largemouth bass when using a high cottonseed protein diet.

## Contribution

The novel finding is that hydrolysable tannin alleviates intestinal inflammation and growth suppression in largemouth bass via NF-κB and arachidonic acid pathways.

## Key findings

- Hydrolysable tannin (HT) improved growth and intestinal health in largemouth bass fed a high cottonseed protein diet.
- HT reduced pro-inflammatory metabolites like PGF2α and LTB4 and suppressed NF-κB signaling pathway activation.
- Digestive enzyme activity and antioxidant capacity were enhanced with HT supplementation.

## Abstract

To more effectively address the scarcity resources and elevated costs associated with fishmeal (FM), the utilization of cottonseed protein concentrate (CPC) as an alternative in aquaculture feeds has become increasingly prevalent. However, high levels of CPC substitution for FM have been reported to suppress the growth of fish and impair intestinal health. Hydrolysable tannin (HT) has been reported to exhibit biological activities such as anti-inflammatory and antioxidant activities, but whether the HT can generate positive biological effects on the intestinal health of largemouth bass (Micropterus salmoides) remains unknown. Largemouth bass (initial weight: 6.03 ± 0.01 g) were subjected to an 8-week feeding trial with three different diets: a basic diet (named as the NC), a high CPC diet (in which CPC replaced 75% of the FM protein in the NC diet, named as the HC), and an additive diet (1.25 g/kg of the HT was added to the HC diet, named as the HCH) to explore the potential benefits of HT on intestinal health.

The HC treatment significantly reduced the weight gain rate of fish, increased the feed conversion ratio, and induced intestinal inflammation. However, the HCH treatment could alleviate the adverse impacts of the HC diet, as evidenced by the promotion of growth and feed utilization, increased activity of digestive enzymes and antioxidant capacities, downregulated expression of pro-inflammatory factors, and maintenance of the integrity of intestinal barrier. Metabolomic analysis revealed that HCH treatment could reduce the pro-inflammatory active substances produced by arachidonic acid metabolism, including prostaglandin F2α (PGF2α) and leukotriene B4 (LTB4). Transcriptomic results indicated that dietary HT might alleviate intestinal inflammation by suppressing the activation of the NF-κB signaling pathway. Furthermore, correlation analysis demonstrated that the metabolites PGF2α and LTB4, derived from arachidonic acid, exhibited a significant positive correlation with the expression of genes associated with pro-inflammatory responses within the NF-κB signaling pathway.

The study indicates that the HT mitigates the growth retardation and intestinal inflammation resulting from the HC diet on largemouth bass.

The online version contains supplementary material available at 10.1186/s40104-025-01267-w.