Micron scale cellulose materials are "generally regarded as safe" (GRAS) as binders and thickeners in food products. However, nanocellulose materials, which have unique properties that can improve food quality and safety, have not received US-Food and Drug Administration (FDA) approval as food ingredients. In vitro and in vivo toxicological studies of ingested nanocellulose revealed minimal cytotoxicity, and no subacute in vivo toxicity. However, ingested materials may modulate gut microbial populations, or alter aspects of intestinal function not elucidated by toxicity testing, which could have important health implications. Here, we report the results of studies conducted in a rat gavage model to assess the effects of ingested cellulose nanofibrils (CNF) on the fecal microbiome and metabolome, intestinal epithelial expression of cell junction genes, and ileal cytokine production. Feces, plasma, and ilea were collected from Wistar Han rats before and after five weeks of biweekly gavages with water or cream, with or without 1% CNF. CNF altered microbial diversity, and diminished specific species that produce short chain fatty acids, and that are associated with increased serum insulin and IgA production. CNF had few effects on the fecal metabolome, with significant changes in only ten metabolites of 366 measured. Exposure to CNF also altered expression of epithelial cell junction genes, and increased production of cytokines that modulate proliferation of CD8 T cells. These perturbations likely represent initiation of an adaptive immune response, however, no associated pathology was seen within the duration of the study. Additional studies are needed to better understand the health implications of these changes in long term.

中文翻译：

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摄入纳米纤维素对 Wistar Han 大鼠肠道微生物群和体内平衡的影响

微米级纤维素材料作为食品中的粘合剂和增稠剂被“普遍认为是安全的”（GRAS）。然而，具有可提高食品质量和安全性的独特特性的纳米纤维素材料尚未获得美国食品和药物管理局 (FDA) 的批准作为食品成分。摄入的纳米纤维素的体外和体内毒理学研究表明细胞毒性很小，没有亚急性体内毒性。然而，摄入的材料可能会调节肠道微生物种群，或改变毒性测试未阐明的肠道功能方面，这可能对健康产生重要影响。在这里，我们报告了在大鼠灌胃模型中进行的研究结果，以评估摄入的纤维素纳米纤维 (CNF) 对粪便微生物组和代谢组的影响，细胞连接基因的肠上皮表达和回肠细胞因子的产生。在每两周灌胃水或乳膏（含或不含 1% CNF）五周之前和之后，从 Wistar Han 大鼠身上收集粪便、血浆和回肠。CNF 改变了微生物多样性，减少了产生短链脂肪酸的特定物种，这些物种与血清胰岛素和 IgA 的产生增加有关。CNF 对粪便代谢组的影响很小，测量的 366 种代谢物中仅 10 种代谢物发生显着变化。暴露于 CNF 还改变了上皮细胞连接基因的表达，并增加了调节 CD8 T 细胞增殖的细胞因子的产生。这些扰动可能代表适应性免疫反应的开始，然而，在研究期间没有发现相关的病理学。