探索臺灣嬰幼兒腸道菌相與疾病之關聯性

Abstract

研究背景: 近年來愈來愈多研究發現嬰幼兒的腸道菌相與他們的健康息息相關。新生兒和嬰兒時期是腸道菌發展的重要時期，此階段的變化可能會影響以後甚至是成人的健康。所以進一步瞭解生命早期的腸道菌群是如何影響我們的發育，有機會找到預防疾病的新療法。因此，本研究的目的為比較足月兒、早產兒、異位性皮膚炎(過敏兒)和發育遲緩兒之間的腸道菌相組成與差異，並且探討腸道菌對兒童疾病的影響。 研究方法: 研究個案來自台大醫院小兒部，於2021年6月開始收樣。在嬰兒大約6個月大時採集尿布上的糞便，接著萃取DNA並進行散彈槍總體基因體定序與進行相對豐富度分析，而後將327名嬰兒腸道菌相結果依據醫師臨床診斷結果，分為過敏兒、早產兒、發育遲緩兒和足月兒等四個組別，透過評估組內和組間的菌種多樣性，計算菌種相對豐富度來了解各組別的菌相分布，和使用線性判別分析效應量(LEfSe)尋找足月兒與其他兩組(過敏兒、遲緩兒)之間具有顯著差異豐度的物種，最後進行功能分析推斷腸道菌的潛在功能。 研究結果: 早產兒的alpha和beta多樣性顯著高於其餘三組，且在門和種的分類層級上相對豐度圖顯示過敏兒、發育遲緩兒和足月兒在六個月大時的腸道菌群組成相似。本研究發現相較足月兒，Ruminococcus gnavus等菌在發育遲緩兒有較高的相對豐富度，而Akkermansia muciniphila等菌則在過敏兒中有較高的相對豐富度。透過功能分析發現腸道菌的潛在功能，在過敏兒和足月兒、以及發育遲緩兒和足月兒之間存在差異。足月兒在參與五個與輔因子和維生素代謝以及四個氨基酸代謝相關的基因豐度皆較過敏兒高，而發育遲緩兒相較於足月兒，其與麩胺酸神經元、GABA神經傳導物質和升糖素傳導途徑相關的功能基因豐度較低。 結論: 在臺灣嬰兒族群中，過敏兒、發育遲緩兒與足月兒在六個月大時的腸道菌相組成很相似。在不同組別間，特定菌種的相對豐富度存在顯著差異，根據LEfSe的結果所發現之特定的菌種，可能具有潛力成為檢測異位性皮膚炎的生物標記。此外，在本研究中也觀察到不同組別之間在生物功能豐度上呈現顯著差異，這些發現都暗示了腸道菌相可能在兒童疾病發生中扮演相關的角色，且這些不同之處可以做為未來兒童疾病研究的重要標的。

Background: It is well-known that the gut microbiota is associated with the health status of infants. The newborn and infant stages are important periods for the development of the intestinal flora, and alterations during this time can impact their future health, even into adulthood. Understanding how gut microbiota affects the development of the human body and mental health may potentially provide new insights into pathogenic mechanisms and uncover therapeutic targets. Therefore, this study aims to investigate gut microbiota profiles and composition among term, preterm, atopic dermatitis (allergic), and developmentally delayed infants in comparison. Additionally, the effects of gut microbiota on the development of pediatric diseases were explored. Materials and Methods: Participants were started enrolled in June, 2021 from the Department of Pediatrics at the National Taiwan University Hospital. Stool specimens were collected when infants were approximately six months old, and whole genome sequences of the extracted DNA from fecal samples were obtained using shotgun metagenomic sequencing for relative abundance analysis. Then, the 327 samples were divided into four groups based on clinical information. We investigated the composition of gut microbiota among groups by assessing the diversity within a sample, estimating the diversity between the samples, and calculating the relative abundance of taxa. Moreover, linear discriminant analysis effect size (LEfSe) was performed to identify taxa with significant differences between the term group and the other two groups (allergy and retardation). Finally, functional analysis was conducted to explore the potential functions of gut microbiota. Results: The alpha and beta diversity values of the preterm infants were significantly higher than those obtained from the other three groups. The relative abundance plot at the phylum and species level showed that the composition of the gut microbiota in the allergic, retardation, and term groups was similar at six months old. In this study, we found that the bacterium of Ruminococcus gnavus was enriched in the retarded infants, whereas the bacterium of Akkermansia muciniphila was enriched in the infants with atopic dermatitis. Furthermore, the analysis of microbial functional genes used to investigate the potential function of taxa showed differences between allergic and term infants, as well as between retarded and term infants. Specially, we found that 5 cofactors and vitamins genes and 4 amino acid metabolism genes were higher in term infants compared to those in allergic infants. Moreover, we also observed a significantly lower abundance of genes related to glutamatergic synapse, GABAergic synapse, and glucagon signaling pathway in the retarded infants in comparison to that in the term infants. Conclusion: Our study revealed that allergic, retarded, and term infants in Taiwan at about six months old exhibited similar gut microbiota profiles. However, there were significant differences in the relative abundance of specific taxa between the allergy and term group, as well as the retardation and term group. Notably, the taxa identified by LEfSe may serve as potential biomarkers for identifying atopic dermatitis. Furthermore, we also found that the abundance of microbial functional genes was different between the groups. These differences in gut microbiota may reveal that they play an important role in pediatric disease and have a potential contribution to the development of pediatric diseases.