In vitro and animal experiments reported a microbiota-regulating ability of oatmeal, however, related in vivo evidences remained limited. Thus, we conducted this study aiming to investigate the oatmeal-induced alteration of gut microbiota and its potential relationship with the improvements of lipid profiles. Data of anthropometric measurements and biochemical parameters were extracted from a randomized, controlled clinical trial, in which 62 hypercholesterolemic men and women (18–65 years old) were provided with either treatment of 80 g/day oatmeal or 80 g/day refined white rice for 45 days. Fasting blood samples and fecal samples were collected both at baseline and endpoint of the study for lipid profiling and microbiota 16S rRNA amplicon sequencing, respectively. Totally 28 participants (56 fecal samples) qualified with the new criteria and were thus included in this secondary analysis. The results of microbiota analysis showed that no significant difference was observed in the alteration of its overall α or β diversity between two groups throughout the study. Nor did any notable between-group difference was found in the relative abundance changes of microorganism at different taxonomies. However, results from linear discriminant analysis effect size in the oatmeal group indicated a significant positive response of Firmicutes phylum following oatmeal consumption. Further Procrustes analysis suggested a concordance trend between microorganism alteration and alleviation of hypercholesterolemia phenotypes throughout the study (P = 0.05). The results of within-group comparison from Spearman’s correlation in the oatmeal group demonstrated a significant association between the enrichment of Blautia genus and the reduction of serum total cholesterol (P < 0.05), low-density lipoprotein cholesterol (P < 0.01), and apolipoprotein B (P < 0.05). Positive response of Firmicutes phylum might be a critical characteristic of oatmeal-induced alteration of microbiota, whereas, one of the underlying cholesterol-lowering mechanism of oatmeal consumption might be its microbiota-manipulating ability, in which the enrichment of Blautia genus played a potentially significant role. Current results should be taken cautiously and more studies were needed for further verification. Trial registration: ChiCTR, ChiCTR180001864. Registered 30 September 2018, http://www.chictr.org.cn/showproj.aspx?proj=31469 .

中文翻译：

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燕麦诱导的肠道微生物群改变及其与改善血脂的关系：一项随机临床试验的二次分析

体外和动物实验报告了燕麦片的微生物群调节能力，然而，相关的体内证据仍然有限。因此，我们进行了这项研究，旨在研究燕麦诱导的肠道微生物群改变及其与脂质谱改善的潜在关系。从一项随机对照临床试验中提取人体测量数据和生化参数，其中 62 名高胆固醇血症男性和女性（18-65 岁）接受 80 克/天燕麦片或 80 克/天精制白米治疗45天。在研究的基线和终点分别收集空腹血液样本和粪便样本，用于脂质分析和微生物群 16S rRNA 扩增子测序。共有 28 名参与者（56 个粪便样本）符合新标准，因此被纳入本次分析。微生物群分析结果表明，在整个研究过程中，两组之间其整体α或β多样性的改变没有显着差异。不同分类微生物的相对丰度变化也没有发现任何显着的组间差异。然而，燕麦组中线性判别分析效应大小的结果表明，在食用燕麦后，厚壁菌门有显着的积极反应。进一步的 Procrustes 分析表明，在整个研究过程中，微生物改变与高胆固醇血症表型缓解之间存在一致趋势 (P = 0.05)。燕麦组 Spearman 相关性的组内比较结果表明，Blautia 属的富集与血清总胆固醇（P < 0.05）、低密度脂蛋白胆固醇（P < 0.01）和载脂蛋白的降低之间存在显着关联乙（P < 0.05）。Firmicutes phylum 的积极反应可能是燕麦诱导的微生物群改变的一个关键特征，而燕麦消费的潜在降胆固醇机制之一可能是其微生物群操纵能力，其中 Blautia 属的富集发挥了潜在的显着意义角色。目前的结果应该谨慎对待，需要更多的研究来进一步验证。试用注册：ChiCTR，ChiCTR180001864。2018年9月30日注册，http://www.chictr.org.cn/showproj。