设计了含有8％纤维素、低甲酯化果胶（LMP）、高甲酯化果胶（HMP）和MMP（一半LMP和一半HMP）的四种饮食，以评估果胶不同甲酯化程度通过不同机制调控鲈鱼肠道微生物群落及其代谢产物对鲈鱼肠道健康的潜在作用机制。结果表明，膳食中的LMP和HMP均持续上调肠道缝蛋白1（ZO-1）、Claudin-1和Claudin-4的表达，并下调肠道肿瘤坏死因子-α（TNF-α）、白细胞介素-8（IL-8）和白细胞介素-1β（IL-1β）基因的表达（P < 0.05）。膳食中的HMP分别上调了肠道阻断素（Occludin）、红细胞生成素2相关因子（Nrf2）、B细胞淋巴瘤-2（Bcl-2）和细胞死亡相关促进因子（BAD）基因的表达，以及消化物丙酸盐含量、操作性税单式节目（OTUs）、Sobs、Shannon、Chao和ACE指数（P < 0.05），而膳食中的LMP降低了消化物精氨酸、4-氨基丁酸、L-酪氨酸和苯丙氨酸含量（P < 0.05）。此外，膳食中的HMP降低了血浆内毒素和d-乳酸含量，提高了肠道超氧化物歧化酶和谷胱甘肽过氧化物酶活性以及免疫球蛋白（Ig）受体和IgM水平（P < 0.05）。总之，膳食中的HMP通过增加肠道菌群α多样性和增强肠道机械屏障、抗炎、抗氧化和免疫功能来改善肠道健康。相反，膳食中的LMP与丁酸盐、酪氨酸、精氨酸和4-氨基丁酸代谢的干扰主要是其对肠道健康的有害作用的原因。版权所有© 2023年。Elsevier B.V.出版。

Four diets containing 8 % cellulose, low methyl-esterified pectin (LMP), high methyl-esterified pectin (HMP) and MMP (half LMP and half HMP) were designed to evaluate the potential mechanisms by which different esterification degrees of pectin drive intestinal microbiota and their metabolites modulating the intestinal health of Micropterus salmoides. The results showed that both dietary LMP and HMP consistently upregulated intestinal zonula occludens protein 1 (Zo-1), Caludin-1, and Caludin-4, and downregulated intestinal tumor necrosis factor-alpha (TNF-α), interleukin-8 (IL-8), and interleukin-1 beta (IL-1β) gene expression (P < 0.05). Dietary HMP separately upregulated intestinal Occludin, nuclear factor erythroid2-related factor 2 (Nrf2), B-cell lymphoma-2 (Bcl-2), and Bcl-2 associated agonist of cell death (BAD) gene expression, as well as the digesta propionate content, OTUs, Sobs, Shannon, Chao, and ACE indices (P < 0.05), whereas dietary LMP decreased digesta arginine, 4-aminobutyric, L-tyrosine, and phenylalanine contents (P < 0.05). Moreover, dietary HMP decreased plasma lipopolysaccharide and d-lactic acid contents and increased intestinal superoxide dismutase and glutathione peroxidase activities and immunoglobulin (Ig) receptor and IgM levels (P < 0.05). Collectively, dietary HMP improves intestinal health by increasing intestinal flora α-diversity and enhancing intestinal mechanical barrier, anti-inflammatory, antioxidant, and immune functions. On the contrary, the interference of dietary LMP with butyrate, tyrosine, arginine, and 4-aminobutyric acid metabolism is the main reason for its detrimental effects on intestinal health.Copyright © 2023. Published by Elsevier B.V.