Takihara Hayato, Okuda Shujiro
Medical AI Center, Niigata University School of Medicine, Niigata, Niigata, Japan.
Front Mol Biosci. 2023 Jun 15;10:1137303. doi: 10.3389/fmolb.2023.1137303. eCollection 2023.
Interactions between humans and the gut microbiome occur by supplying nutrients to gut epithelial cells via short-chain fatty acids obtained from dietary carbohydrates or mucins and activating immunity via mucins' degradation. The degradation of carbohydrates derived from food is an important function for organisms to obtain energy. However, since humans possess only 17 genes encoding carbohydrate-degrading enzymes, the gut microbiome is responsible for degrading plant-derived polysaccharides. Using the method for extracting glycan-related genes from the metagenomes constructed thus far, we calculated the distribution and abundance of different glycan-related genes in the healthy human gut metagenome. Glycan-related genes showed an abundance of 0.64-11.00, indicating large individual differences. However, the distribution of the classes of glycan-related genes was similar between the samples. In addition, the function of carbohydrate degradation was divided into three clusters, showing high diversity; however, the synthesis function was not divided, indicating low diversity. The substrates of enzymes for carbohydrate degradation between clusters were either plant-derived polysaccharides or biased toward degrading polysaccharides derived from other sources. These functional biases differ depending on the type of microorganism used. Based on these findings, we predicted that 1) diversity will be constant because the influence on the host by the transferase of gut bacteria is a function derived from the genome, and 2) diversity will be high because the influence on the host by the hydrolase of gut bacteria is affected by incoming dietary carbohydrates.
通过从膳食碳水化合物或粘蛋白中获取的短链脂肪酸为肠道上皮细胞提供营养，并通过粘蛋白的降解激活免疫。食物中碳水化合物的降解是生物体获取能量的一项重要功能。然而，由于人类仅拥有17个编码碳水化合物降解酶的基因，因此肠道微生物群负责降解植物来源的多糖。利用从迄今为止构建的宏基因组中提取聚糖相关基因的方法，我们计算了健康人类肠道宏基因组中不同聚糖相关基因的分布和丰度。聚糖相关基因的丰度为0.64 - 11.00，表明个体差异较大。然而，样本之间聚糖相关基因类别的分布相似。此外，碳水化合物降解功能分为三个簇，显示出高度多样性；然而，合成功能未分类，表明多样性较低。不同簇之间碳水化合物降解酶的底物要么是植物来源的多糖，要么偏向于降解其他来源的多糖。这些功能偏差因所使用的微生物类型而异。基于这些发现，我们预测：1）多样性将保持恒定，因为肠道细菌转移酶对宿主的影响是源自基因组的一种功能；2）多样性将很高，因为肠道细菌水解酶对宿主的影响受摄入的膳食碳水化合物影响。
