Dietary rice bran (RB) has shown capacity to influence metabolism by modulation of gut microbiota in individuals at risk for colorectal cancer (CRC), which warranted attention for delineating mechanisms for bidirectional influences and cross-feeding between the host and RB-modified gut microbiota to reduce CRC. Accordingly, in the present study, fermented rice bran (FRB, fermented with a RB responsive microbe Bifidobacterium longum), and non-fermented RB were fed as 10% w/w (diet) to gut microbiota-intact^spf or germ-free mice^gf to investigate comparative efficacy against inflammation-associated azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC. Results indicated both microbiota-dependent and independent mechanisms for RB meditated protective efficacy against CRC that was associated with reduced neoplastic lesion size and local-mucosal/systemic inflammation, and restoration of colonic epithelial integrity. Enrichment of beneficial commensals (such as, Clostridiales, Blautia, Roseburia), phenolic metabolites (benzoate and catechol metabolism), and dietary components (ferulic acid-4 sulfate, trigonelline, and salicylate) were correlated with anti-CRC efficacy. Germ-free studies revealed gender-specific physiological variables could differentially impact CRC growth and progression. In the germ-free females, the RB dietary treatment showed a ∼72% reduction in the incidence of colonic epithelial erosion when compared to the ∼40% reduction in FRB-fed mice^gf. Ex vivo fermentation of RB did not parallel the localized-protective benefits of gut microbial metabolism by RB in damaged colonic tissues. Findings from this study suggest potential needs for safety considerations of fermented fiber rich foods as dietary strategies against severe inflammation-associated colon tumorigenesis (particularly with severe damage to the colonic epithelium).

中文翻译：

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肠道微生物群缺失对长双歧杆菌发酵米糠饮食对炎症相关结肠肿瘤发生的保护功效的性别影响

膳食米糠 (RB) 已显示出通过调节肠道微生物群影响结直肠癌 (CRC) 风险个体代谢的能力，这值得关注宿主和 RB 修饰的肠道微生物群之间双向影响和交叉喂养的机制以减少CRC。因此，在本研究中，发酵米糠（FRB，用 RB 反应性微生物长双歧杆菌发酵）和未发酵的 RB 以 10% w/w（饮食）喂养肠道微生物群完整的^spf或无菌小鼠^gf研究对炎症相关氧化偶氮甲烷/葡聚糖硫酸钠 (AOM/DSS) 诱导的 CRC 的比较功效。结果表明，微生物群依赖性和独立机制对 RB 介导的对 CRC 的保护功效与肿瘤病变大小和局部粘膜/全身炎症的减少以及结肠上皮完整性的恢复有关。有益共生菌（如梭状芽胞杆菌、布劳氏菌、罗斯氏菌）、酚类代谢物（苯甲酸盐和儿茶酚代谢）和膳食成分（阿魏酸-4硫酸盐、葫芦巴碱和水杨酸盐）的富集与抗结直肠癌功效相关。无菌研究表明，性别特异性生理变量可能对结直肠癌的生长和进展产生不同的影响。在无菌雌性小鼠中，RB 饮食治疗显示结肠上皮糜烂的发生率降低了约 72%，而 FRB 喂养的小鼠结肠上皮糜烂的发生率降低了约 40 ^%。RB 的离体发酵与 RB 在受损结肠组织中肠道微生物代谢的局部保护作用并不相似。这项研究的结果表明，潜在需要考虑富含纤维的发酵食品的安全性，作为对抗严重炎症相关结肠肿瘤发生（特别是结肠上皮严重损伤）的饮食策略。