GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Toulouse, France.
Université Paris-Saclay, AgroParisTech, INRAE, UMR PNCA, Paris, France.
Adv Exp Med Biol. 2020;1265:1-20. doi: 10.1007/978-3-030-45328-2_1.
Dietary protein digestion is an efficient process resulting in the absorption of amino acids by epithelial cells, mainly in the jejunum. Some amino acids are extensively metabolized in enterocytes supporting their high energy demand and/or production of bioactive metabolites such as glutathione or nitric oxide. In contrast, other amino acids are mainly used as building blocks for the intense protein synthesis associated with the rapid epithelium renewal and mucin production. Several amino acids have been shown to support the intestinal barrier function and the intestinal endocrine function. In addition, amino acids are metabolized by the gut microbiota that use them for their own protein synthesis and in catabolic pathways releasing in the intestinal lumen numerous metabolites such as ammonia, hydrogen sulfide, branched-chain amino acids, polyamines, phenolic and indolic compounds. Some of them (e.g. hydrogen sulfide) disrupts epithelial energy metabolism and may participate in mucosal inflammation when present in excess, while others (e.g. indole derivatives) prevent gut barrier dysfunction or regulate enteroendocrine functions. Lastly, some recent data suggest that dietary amino acids might regulate the composition of the gut microbiota, but the relevance for the intestinal health remains to be determined. In summary, amino acid utilization by epithelial cells or by intestinal bacteria appears to play a pivotal regulator role for intestinal homeostasis. Thus, adequate dietary supply of amino acids represents a key determinant of gut health and functions.
膳食蛋白质的消化是一个高效的过程，其结果是上皮细胞吸收氨基酸，主要是在空肠。一些氨基酸在肠细胞中被广泛代谢，以支持其高能量需求和/或生物活性代谢物如谷胱甘肽或一氧化氮的产生。相比之下，其他氨基酸主要用作与快速上皮细胞更新和粘蛋白产生相关的强烈蛋白质合成的构建块。已经有研究表明，一些氨基酸可以支持肠道屏障功能和肠内分泌功能。此外，氨基酸被肠道微生物群代谢，微生物群利用它们进行自身的蛋白质合成，并在代谢途径中释放大量代谢物到肠腔中，如氨、硫化氢、支链氨基酸、多胺、酚类和吲哚类化合物。其中一些（如硫化氢）破坏上皮细胞的能量代谢，并可能在过量存在时参与粘膜炎症，而另一些（如吲哚衍生物）则可以防止肠道屏障功能障碍或调节肠内分泌功能。最后，一些最近的数据表明，膳食氨基酸可能调节肠道微生物群的组成，但这对肠道健康的相关性仍有待确定。总之，上皮细胞或肠道细菌对氨基酸的利用似乎对肠道内稳态起着关键的调节作用。因此，膳食中提供足够的氨基酸是肠道健康和功能的关键决定因素。
