大豆皂苷通常被认为对水生动物的生长和肠道有负面影响，而适当水平的丁酸钠（NaB）可能具有一定的缓解效果。我们研究了低水平和高水平的大豆皂苷以及丁酸钠的保护效果（基于高水平的大豆皂苷）对杂交石斑鱼（Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂）生长、血清细胞因子、远端肠道组织病理和炎症的影响。实验包括四个组：鱼粉组（FM，0.00% 皂苷和 0.00% NaB）、低皂苷组（SL，0.30% 皂苷和 0.00% NaB）、高皂苷组（SH，1.50% 皂苷和 0.00% NaB）和高皂苷与 NaB 组（SH-NaB，1.50% 皂苷和 0.13% NaB）。结果显示与 FM 相比，最终体重（FBW）和体重增加（WG）在 SL 和 SH 中分别显著增加和降低（P < 0.05）。与 SH 相比，在 SH-NaB 组中 FBW 和 WG 显著增加（P < 0.05）。在血清中，与 FM 相比，SH 中干扰素γ（IFN-γ）和白细胞介素-1β（IL-1β）水平显著增加（P < 0.05）。与 SH 相比，在 SH-NaB 中 IFN-γ 水平显著降低（P < 0.05）。在远端肠道中，根据Alcian Blue-Periodic Acid-Schiff（AB-PAS）观察，与 FM 相比，SL 和 SH 中的粘液细胞/μm显著增加和降低，肠褶高度比在 SH 中显著高于 FM、SL 和 SH-NaB（P < 0.05）。SH 中的 NO 和 ONOO- 水平显著高于 FM 和 SL（P < 0.05）。在远端肠道的转录水平上，与 FM 相比，在 SH 中肿瘤坏死因子（tnfα）、白细胞介素-1β（il1β）、白细胞介素-8（il8）和干扰素γ（ifnγ）的 mRNA 水平显著上调（P < 0.05）。与 SH 相比，在 SH-NaB 中 tnfα、il8 和 ifnγ 的 mRNA 水平显著下调（P < 0.05）。与 FM 相比，在 SL 中 claudin3、claudin15、zo2 和 zo3 的 mRNA 水平显著上调（P < 0.05）。与 FM 相比，在 SH 中 occludin、claudin3、claudin12、claudin15、zo1、zo2 和 zo3 的 mRNA 水平显著下调（P < 0.05）。此外，与 SH 相比，在 SH-NaB 中 occludin、claudin3、claudin12、claudin15、zo1、zo2 和 zo3 的 mRNA 水平显著上调（P < 0.05）。经过为期 7 天的副溶血性弧菌挑战实验，与 FM 相比，SL 的存活率显著更高，SH 的存活率显著更低（P < 0.05）。总体而言，低水平和高水平的大豆皂苷分别对杂交石斑鱼的生长、抗病性、血清细胞因子和远端肠道发育和抗炎症产生了正面和负面影响。NaB 能有效增强疾病抵抗力，并改善杂交石斑鱼的远端肠道炎症，但其主要在改善远端肠道紧密连接中发挥作用。Copyright © 2023. Published by Elsevier Ltd.

Soy saponins are generally known to have negative effects on growth and the intestines of aquatic animals, and appropriate levels of sodium butyrate (NaB) may provide some mitigating effects. We investigated the effects of low and high levels of soy saponin and the protective effects of NaB (based on high level of soy saponin) on growth, serum cytokines, distal intestinal histopathology, and inflammation in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). The experiment included four groups: fishmeal group (FM, 0.00% saponin and 0.00% NaB), low saponin group (SL, 0.30% saponin and 0.00% NaB), high saponin group (SH, 1.50% saponin and 0.00% NaB) and high saponin with NaB group (SH-NaB, 1.50% saponin and 0.13% NaB). The results showed compared to FM, the final body weight (FBW) and weight gain (WG) were significantly higher and lower in SL and SH, respectively (P < 0.05). Compared to SH, the FBW and WG were significant higher in SH-NaB (P < 0.05). In the serum, compared to FM, the interferon γ (IFN-γ) and interleukin-1β (IL-1β) levels in SH were significantly increased (P < 0.05). Compared to SH, the IFN-γ level was significantly decreased in SH-NaB (P < 0.05). In the distal intestine, based on Alcian Blue-Periodic Acid-Schiff (AB-PAS) observation, the goblet cell/μm was significantly increased and decreased in the SL and SH, respectively, compared to FM. The intestinal diameter/plica height ratio in the SH was significantly higher than those in the FM, SL and SH-NaB (P < 0.05). The NO and ONOO- levels in the SH were significantly higher than that in FM and SL (P < 0.05). At the transcriptional level in the distal intestine, compared to FM, the mRNA levels of tumor necrosis factor (tnfα), il1β, interleukin-8 (il8) and ifnγ were significantly up-regulated in the SH (P < 0.05). Compared to the SH, tnfα, il8 and ifnγ were significantly down-regulated in the SH-NaB (P < 0.05). Compared to the FM, the mRNA levels of claudin3, claudin15, zo2 and zo3 were significantly up-regulated in the SL (P < 0.05). The mRNA levels of occludin, claudin3, claudin12, claudin15, zo1, zo2 and zo3 were significantly down-regulated in the SH compared to the FM (P < 0.05). Additionally, compared to the SH, the mRNA levels of occludin, claudin3, claudin12, claudin15, zo1, zo2 and zo3 were significantly up-regulated in the SH-NaB (P < 0.05). After the 7-day Vibrio parahaemolyticus challenge test, the survival was significantly higher and lower in the SL and SH, respectively, compared to FM (P < 0.05). Overall, low and high levels of soy saponins had positive and negative effects on growth, disease resistance, serum cytokines, and distal intestinal development and anti-inflammation, respectively, in hybrid grouper. NaB effectively increased disease resistance and improved distal intestinal inflammation in hybrid grouper, but the effects of NaB were mainly observed in improving distal intestinal tight junctions.Copyright © 2023. Published by Elsevier Ltd.