BACKGROUND Previous studies have reported gut microbiome alterations in Hashimoto's autoimmune thyroiditis (HT) patients. Yet, it is unknown whether an aberrant microbiome is present before clinical disease onset in participants susceptible to HT or whether it reflects the effects of the disease itself. Here, we report for the first time a comprehensive characterization of the taxonomic and functional profiles of the gut microbiota in euthyroid seropositive and seronegative participants. Our primary goal was to determine taxonomic and functional signatures of the intestinal microbiota associated with serum thyroid peroxidase antibodies (TPOAb) antibodies. A secondary aim was to determine whether different ethnicities warrant distinct reference intervals for accurate interpretation of serum thyroid biomarkers. METHODS In this cross-sectional study, euthyroid participants with (N=159) and without (N=1,309) TPOAb were selected from the multi-ethnic (European Dutch, Moroccan, and Turkish) HEalthy Life In an Urban Setting (HELIUS) cohort. Fecal microbiota composition was profiled using 16S rRNA sequencing. Differences between the groups were analyzed based on overall composition (alpha and beta diversity), as well as differential abundance of microbial taxa and functional pathways using multiple differential abundance tools. RESULTS Overall composition showed a substantial overlap between the two groups (p>0.05 for alpha-diversity; p=0.39 for beta-diversity), indicating that TPOAb-seropositivity does not significantly differentiate gut microbiota composition and diversity. Interestingly, TPOAb-status accounted for only a minor fraction (0.07%) of microbiome variance (p=0.545). Further exploration of taxonomic differences identified 138 taxa nominally associated with TPOAb-status. Among these, thirteen taxa consistently demonstrated nominal significance across three additional differential abundance methods, alongside notable associations within various functional pathways. Furthermore, we showed that ethnicity-specific reference intervals for serum thyroid biomarkers are not required, as no significant disparities in serum thyroid markers were found among the three ethnic groups residing in an iodine-replete area (p>0.05 for TSH, fT4, and TPOAb). CONCLUSION These findings suggest that there is no robust difference in gut microbiome between individuals with or without TPOAb in terms of alpha and beta-diversity. Nonetheless, several taxa were identified with nominal significance related to TPOAb presence. Further research is required to determine whether these changes indeed imply a higher risk of overt HT.

中文翻译：

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甲状腺功能正常的参与者中与甲状腺过氧化物酶抗体血清转化相关的分类学和功能性肠道微生物群概况的比较分析。

背景先前的研究已经报道了桥本自身免疫性甲状腺炎（HT）患者肠道微生物组的改变。然而，尚不清楚易患 HT 的参与者在临床疾病发作之前是否存在异常微生物组，或者它是否反映了疾病本身的影响。在这里，我们首次报告了甲状腺功能正常的血清阳性和血清阴性参与者肠道微生物群的分类和功能特征的全面表征。我们的主要目标是确定与血清甲状腺过氧化物酶抗体 (TPOAb) 抗体相关的肠道微生物群的分类学和功能特征。第二个目的是确定不同种族是否需要不同的参考区间来准确解释血清甲状腺生物标志物。方法 在这项横断面研究中，从多民族（欧洲荷兰人、摩洛哥人和土耳其人）城市环境健康生活 (HELIUS) 队列中选择具有 (N=159) 和不具有 (N=1,309) TPOAb 的甲状腺功能正常的参与者。使用 16S rRNA 测序分析粪便微生物群组成。根据整体组成（α和β多样性）以及微生物类群的差异丰度和使用多种差异丰度工具的功能途径分析各组之间的差异。结果 总体组成显示两组之间存在显着重叠（α 多样性 p>0.05；β 多样性 p=0.39），表明 TPOAb 血清阳性并不能显着区分肠道微生物群组成和多样性。有趣的是，TPOAb 状态仅占微生物组变异的一小部分 (0.07%) (p=0.545)。进一步探索分类学差异，确定了 138 个名义上与 TPOAb 状态相关的分类群。其中，十三个类群在另外三种差异丰度方法中始终表现出名义意义，同时在各种功能途径中也具有显着的关联。此外，我们表明，不需要血清甲状腺生物标志物的种族特异性参考区间，因为居住在碘充足地区的三个种族群体之间的血清甲状腺标志物没有发现显着差异（TSH、fT4 和 TSH、fT4 的 p>0.05）。 TPOAb)。结论 这些发现表明，有或没有 TPOAb 的个体之间的肠道微生物组在 α 和 β 多样性方面没有显着差异。尽管如此，几个类群被鉴定为与 TPOAb 存在相关的名义意义。需要进一步的研究来确定这些变化是否确实意味着明显的 HT 风险更高。