Zhang Fengli, Tian Jiajun, Li Jitong, Zhang Tengyuan, Wang Xiao
Department of Aquaculture, Zhejiang Ocean University, Zhoushan, 316000, China.
Department of Aquaculture, Zhejiang Ocean University, Zhoushan, 316000, China.
Fish Shellfish Immunol. 2025 Aug 25;167:110683. doi: 10.1016/j.fsi.2025.110683.
High-fat-induced metabolic syndrome poses many challenges to fish farming. In our previous study, we found that probiotic Akkermansia muciniphila can increase the tryptophan microbiota metabolite indole-3-lactic acid (ILA). Therefore, this study further investigates the effect of ILA on resisting HFD-induced metabolic disorders and preliminarily explores its mechanism in zebrafish. We found that supplementation with 100 μg/g ILA significantly attenuated HFD-induced weight gain, improved feed conversion ratio, and had no effect on survival rate. Additionally, ILA alleviated hepatic steatosis, significantly reducing triglyceride accumulation by downregulating lipogenic genes (DGAT2, SREBP-1c; p < 0.01, p < 0.05), while enhancing the expression of lipolytic gene, such as UCP2 (p < 0.01). Concurrently, ILA preserved intestinal barrier integrity by attenuating intestinal villi damage and restoring tight junction ultrastructure. qRT-PCR results showed that ILA supplementation enhanced both intestinal mechanical and chemical barrier integrity by upregulating tight junction proteins (Muc2, TJP-1α, Cldn12) and complement C3b. Additionally, HFD increased serum LPS and hepatic LBP, which were reversed by ILA. And it could also ameliorate HFD-induced low-grade inflammation, as evidenced by suppressing pro-inflammatory cytokines (TNF-α, IL-6; p < 0.05) while elevating anti-inflammatory IL-10 (p < 0.05). Gut microbiota analysis revealed ILA intake exerted no significant effects on alpha diversity, yet profoundly restructured microbial composition by reducing Bacillota, Bacteroidota abundance and enriching Fusobacteriota, Verrucomicrobiota compared to the HFD group, accompanied by reduced abundance of pathogenic genera (Shewanella, Acinetobacter, Malacoplasma, Culicoidibacter, and Pseudomonas). Transcriptome sequencing analysis identified 3594 differentially expressed genes (DEGs) following ILA supplementation. These DEGs were significantly enriched in lipid metabolism and immune-related pathways, including drug metabolism-cytochrome P450, steroid hormone biosynthesis, fatty acid degradation, glycerolipid metabolism, as well as the PPAR/FoxO/insulin signaling pathways. It was further verified that the effects of ILA could be mediated via AhR2 receptor activation, followed by the modulation of Cyp1a1, a downstream gene involved in drug metabolism-cytochrome P450. Multi-omics analyses revealed significant correlation between gut microbial genera abundance and pathway-specific gene expression. These findings collectively demonstrated that ILA ameliorates HFD-induced metabolic dysfunction through dual regulation of lipid homeostasis, intestinal barrier function, and inflammation, providing insights into its potential mechanisms.
高脂诱导的代谢综合征给鱼类养殖带来了诸多挑战。在我们之前的研究中，我们发现益生菌嗜黏蛋白阿克曼氏菌可以增加色氨酸微生物代谢产物吲哚 - 3 - 乳酸（ILA）。因此，本研究进一步探究ILA对抵抗高脂饮食（HFD）诱导的代谢紊乱的影响，并初步探索其在斑马鱼中的作用机制。我们发现，补充100μg/g的ILA可显著减轻HFD诱导的体重增加，改善饲料转化率，且对存活率无影响。此外，ILA减轻了肝脏脂肪变性，通过下调脂肪生成基因（DGAT2、SREBP - 1c；p < 0.01，p < 0.05）显著减少甘油三酯积累，同时增强了脂解基因如UCP2的表达（p < 0.01）。与此同时，ILA通过减轻肠绒毛损伤和恢复紧密连接超微结构来维持肠道屏障完整性。qRT - PCR结果表明，补充ILA通过上调紧密连接蛋白（Muc2、TJP - 1α、Cldn12）和补体C3b增强了肠道机械和化学屏障的完整性。此外，HFD增加了血清LPS和肝脏LBP，而ILA可使其逆转。并且它还可以改善HFD诱导的低度炎症，表现为抑制促炎细胞因子（TNF - α、IL - 6；p < 0.05），同时升高抗炎性IL - 10（p < 0.05）。肠道微生物群分析显示，摄入ILA对α多样性没有显著影响，但与HFD组相比，通过减少芽孢杆菌门、拟杆菌门的丰度并富集梭杆菌门、疣微菌门，深刻地重塑了微生物组成，同时伴随着致病属（希瓦氏菌属、不动杆菌属、支原体属、库利科迪杆菌属和假单胞菌属）丰度的降低。转录组测序分析确定了补充ILA后有3594个差异表达基因（DEG）。这些DEG在脂质代谢和免疫相关途径中显著富集，包括药物代谢 - 细胞色素P450、类固醇激素生物合成、脂肪酸降解、甘油olipid代谢，以及PPAR/FoxO/胰岛素信号通路。进一步证实，ILA的作用可能是通过激活AhR2受体介导的，随后调节参与药物代谢 - 细胞色素P450的下游基因Cyp1a1。多组学分析揭示了肠道微生物属丰度与途径特异性基因表达之间存在显著相关性。这些发现共同表明，ILA通过对脂质稳态、肠道屏障功能和炎症的双重调节改善了HFD诱导的代谢功能障碍，为其潜在机制提供了见解。
