岩藻多糖改善结肠炎相关性结直肠癌小鼠肠道菌群的16S rRNA测序研究

Fucoidan Modulates Gut Microbiota in CAC Mice Revealed by 16S rRNA Sequencing

摘要: 目的：基于16S rRNA测序系统评估岩藻多糖(fucoidan, FU)对AOM/DSS诱导结肠炎相关性结直肠癌(colitis-associated colorectal cancer, CAC)小鼠肠道菌群多样性、组成及功能潜能的影响，为其改善肠道微生态失衡提供证据。方法：C57BL/6J小鼠建立AOM/DSS诱导CAC模型，分为NC组、AOM/DSS组、FU低剂量组(FL, 600 mg/kg)和FU高剂量组(FH, 1200 mg/kg)。采集结肠内容物提取微生物DNA并进行16S rRNA高通量测序。分析α多样性(Chao1, Observed_species, Faith_pd, Shannon, Simpson, Pielou_e)、β多样性(Bray-Curtis, Jaccard, weighted/unweighted UniFrac, PCoA/NMDS)、属水平菌群组成与差异菌群(LEfSe)，并采用PICRUSt2预测功能谱，结合metagenomeSeq进行差异通路分析。结果：α多样性分析显示，丰富度相关指标在组间差异不显著，而AOM/DSS组的多样性/均匀度指标发生显著改变，提示模型诱导菌群生态结构异常重排；FU干预后相关指标呈一定程度的调整趋势。β多样性分析显示，AOM/DSS组与NC组菌群结构明显分离，FU干预后FL与FH组样本在排序空间中发生位移并呈更集中聚类趋势，提示FU可重塑CAC背景下菌群群落结构。属水平分析与热图结果显示，FU干预可重构优势菌属谱系并形成剂量相关的菌群特征；LEfSe进一步筛选出不同组别的特征菌群标志物。功能预测提示各组以代谢相关模块为主，FU干预可影响整体功能谱结构；差异通路分析显示AOM/DSS相对NC存在多条代谢/转运相关通路异常改变。结论：岩藻多糖可在CAC模型背景下调节肠道菌群多样性与群落结构，重塑特征菌群组成，并影响预测功能与代谢相关通路，提示其改善CAC微生态失衡可能是其发挥保护作用的重要机制之一。

Abstract: To systematically evaluate the effects of fucoidan (FU) on the diversity, composition, and functional potential of the gut microbiota in an azoxymethane/dextran sodium sulfate (AOM/DSS)-induced colitis-associated colorectal cancer (CAC) mouse model based on 16S rRNA sequencing, and to provide evidence for its role in improving intestinal microbial dysbiosis, a CAC model was established in C57BL/6J mice using AOM/DSS, and the animals were divided into four groups: normal control (NC), AOM/DSS model group, fucoidan low-dose group (FL, 600 mg/kg), and fucoidan high-dose group (FH, 1200 mg/kg). Colonic contents were collected for microbial DNA extraction followed by 16S rRNA high-throughput sequencing. Alpha diversity indices (Chao1, Observed_species, Faith_pd, Shannon, Simpson, and Pielou_e) and beta diversity metrics (Bray-Curtis, Jaccard, weighted/unweighted UniFrac, PCoA/NMDS) were analyzed. Genus-level microbial composition and differential taxa were identified using LEfSe analysis, while functional profiles were predicted using PICRUSt2 and differential pathway analysis was performed with metagenomeSeq. The results showed that richness-related alpha diversity indices did not differ significantly among groups, whereas diversity and evenness indices in the AOM/DSS group were markedly altered, indicating an abnormal restructuring of the microbial ecological community induced by the model; these indices showed a tendency toward restoration after FU intervention. Beta diversity analysis revealed a clear separation in microbial community structure between the AOM/DSS and NC groups, while samples in the FL and FH groups shifted in the ordination space and exhibited a more concentrated clustering pattern after FU treatment, suggesting that FU could reshape the gut microbial community structure under CAC conditions. Genus-level composition analysis and heatmap results demonstrated that FU intervention reconstructed dominant bacterial genera and produced dose-dependent microbial characteristics, and LEfSe analysis further identified specific microbial biomarkers among different groups. Functional prediction indicated that metabolic-related modules predominated across groups, and FU intervention influenced the overall functional profile, while differential pathway analysis revealed that multiple metabolism- and transport-related pathways were significantly altered in the AOM/DSS group compared with the NC group. Overall, fucoidan can modulate gut microbiota diversity and community structure in the CAC model, reshape characteristic microbial taxa, and influence predicted microbial functions and metabolism-related pathways, suggesting that the improvement of intestinal microbial dysbiosis may represent an important mechanism underlying the protective effects of fucoidan against CAC.