What question did this study set out to answer?

This research aims to evaluate the effects of tea saponin supplementation on growth and hepatic health in hybrid grouper fed a high-lipid diet.

May 7, 2026Open Access

Tea Saponin Exerts Dose-Dependent Dual Effects on Growth and Hepatic Health in Hybrid Grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) Fed a High-Lipid, Low-Protein Diet via Redox-Immune Regulation

Key Points

This research aims to evaluate the effects of tea saponin supplementation on growth and hepatic health in hybrid grouper fed a high-lipid diet.
Four-week feeding trial on juvenile hybrid grouper with varying tea saponin doses (0% to 0.20%)
Assessment of growth metrics and hepatic health markers
Transcriptomic analysis to identify molecular pathways affected by tea saponin
Low tea saponin (0.05%) improved growth (final average weight) while high doses (≥0.15%) inhibited weight gain
Significant reduction in malondialdehyde and reactive oxygen species at 0.05%, suggesting improved oxidative stress response
Higher superoxide dismutase activity and increased immunoglobulin M levels in lower tea saponin groups confirmed enhanced immune function.

Abstract

High-lipid, low-protein diets are economically advantageous in aquaculture costs but often induce hepatic damage, immunosuppression and metabolic disorders in carnivorous fish like hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). Tea saponin (TS) is a bioactive triterpenoid from camellia seed meal with excellent lipid-lowering and anti-inflammatory effects. The purpose of the current study was to investigate the dose-dependent impacts of TS supplementation at 0% (control, T0), 0.05% (T5), 0.10% (T10), 0.15% (T15), and 0.20% (T20) in diets formulated to contain 42% crude protein and 16% crude lipid on juvenile hybrid grouper (17.51 ± 0.03 g), with three replicate tanks per treatment, over a 4-week feeding trial. The results showed that low TS supplementation (0.05%) improved growth, with the effect limited to final average weight (FAW), whereas higher doses (≥0.15%) reduced weight gain. The T5 group exhibited the highest hepatic total antioxidant capacity and superoxide dismutase activity, consistent with the corresponding gene expression, and the lowest malondialdehyde and reactive oxygen species levels. Lysozyme activity and immunoglobulin M content were significantly higher in T5–T15 groups (p < 0.05). Furthermore, appropriate TS significantly upregulated anti-inflammatory cytokines (p < 0.05) and downregulated pro-inflammatory factors. Histologically, 0.10% TS reduced inflammatory infiltration, while high doses caused hepatocyte rupture and lipid vacuolation. Transcriptomic analysis further elucidated that the beneficial effects of low-dose TS were linked to the activation of PPAR signaling, fatty acid catabolism, and cellular quality control pathways, while high-dose TS triggered stress-related and biosynthetic programs. In conclusion, moderate TS supplementation (0.05–0.10%) ameliorated diet-induced oxidative stress and immunosuppression, improved growth performance and anti-inflammatory factor expression, whereas over-addition inhibited growth and exacerbated hepatic damage. Based on a quadratic model, the optimal dietary TS level for maximizing growth under this low-protein, high-lipid regimen is estimated at 0.055%.

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