人体肠道菌群代谢氨基酸产生短链脂肪酸及对细胞通透性的影响

Human Intestinal Flora Metabolite Short-chain Fatty Acids Produced from Amino Acids and Effect on Cell Permeability

目的:采用肠道微生物体外模拟批式发酵的方法,探究人体肠道微生物对氨基酸代谢特征及其代谢产物对上皮细胞通透性的影响。选取27位年龄在20~55岁健康人的粪便样本,利用常见的20种氨基酸并对照小牛血清蛋白、NaCl培养基,进行24 h体外批次发酵,采用气相色谱检测发酵液中短链脂肪酸的含量。然后,测定氨基酸的短链脂肪酸对Caco-2细胞的跨膜电阻值(TEER)的影响。检测结果表明在含亮氨酸(Leu)和异亮氨酸(Ile)的培养基中,异戊酸产量明显高于对照组(P<0.01);在含缬氨酸(Val)的培养基中,异丁酸水平显著升高(P<0.01);在含脯氨酸(Pro)的培养基中,戊酸产量明显增加(P<0.01)。Caco-2细胞试验表明:戊酸能显著提高Caco-2细胞跨膜电阻值(P<0.01),而异丁酸和异戊酸能显著降低细胞跨膜电阻值。因此,本试验揭示结肠内容物中的异戊酸是由Leu、Ile降解形成;异丁酸是由Val代谢形成;戊酸主要是由Pro代谢产生,并且能够显著增强肠道黏膜屏障功能。

To investigate the feature of amino acids metabolism of human colonic microbes and the influence of their metabolites on the permeability of epithelial cells,in vitro batch fermentation of human gut microbiota was used.The media were based on general 20 amino acids with bovine serum albumin and NaCl as controls.The feces specimen was collected from 27 healthy people aged 20 to 55 years old.The short-chain fatty acids(SCFA)in the broths of 24 h fermentation were detected by gas chromatography.The effects of the amino acids-derived SCFA on the transmembrane resistance of Caco-2 cells was determined.The production of isovaleric acid in the medium containing leucine(Leu)and isoleucine(Ile)was significantly higher than that of the control group(P<0.01).After fermentation of the medium containing valine(Val),the level of isobutyric acid was significantly increased(P<0.01).In the medium containing proline(Pro),the production of valeric acid was significantly increased(P<0.01).The results of the cell line showed that valeric acid can significantly increase the transmembrane resistance of Caco-2 cells(P<0.01),while isobutyric acid and isovaleric acid can significantly reduce the transmembrane resistance.As a conclusion,isovaleric acid in the colon content is formed by the degradation of Leu and Ile;isobutyric acid is formed by the metabolism of Val;valeric acid is mainly formed by the metabolism of Pro.Valeric acid can significantly enhance the intestinal mucosal barrier function.