肠道菌群与NAFLD发生发展的关联代谢机制研究

发布时间：2018-11-04 19:58

【摘要】：研究背景随着肥胖及其相关代谢综合征全球化的流行趋势,非酒精性脂肪性肝病(NAFLD)现已成为威胁全球人类健康的慢性肝病。目前越来越多的研究证据表明肠道菌群(IM)紊乱在NAFLD的发生发展中起重要作用。但相关研究尤其是人群实验数量有限,而且菌群失调如何影响机体代谢尚未见报道。肝脏是参与机体代谢的重要器官,胆汁酸和氨基酸代谢是肝脏的两个主要代谢通路,并且与NAFLD的发生发展相关。我们前期预实验发现NAFLD患者IM显著影响宿主的代谢表型,初步发现胆汁酸和氨基酸代谢异常。因此,本研究将进—步深入探索胆汁酸、氨基酸代谢与IM之间的联系及其在NAFLD发生发展中所起的作用。研究方法本研究以非酒精性脂肪肝(NAFL)、非酒精性脂肪性肝炎(NASH)患者以及健康对照(HC)个体为研究对象;利用分子生态学方法研究NAFLD患者肠道菌群结构和功能改变;通过高效液相色谱—串联质谱法(UPLC-MS/MS)和核磁检测技术(NMR)检测NAFLD患者小分子代谢谱变化,重点检测患者血清和粪便胆汁酸以及血清氨基酸水平;运用生物信息统计分析,初探IM改变与患者胆汁酸和氨基酸代谢变化的潜在关联。研究结果1.从菌群分析结果上看,NASH患者IM结构和功能较NAFL和HC组出现显著变化。NASH组的肠道菌群生物多样性显著降低,菌群结构变化表现为:与HC相比,在门的水平上,NASH患者拟杆菌门显著降低,而变形菌门和放线菌门显著增加;在科的水平上,拟杆菌科在NASH组肠道中降低,而肠杆菌科显著增加;在属的水平上,拟杆菌属在NASH患者肠道中显著降低,而Blautia属显著增加。拟杆菌、肠杆菌科及Blautia属改变与胆汁酸.代谢异常密切相关。通过功能代谢分析发现,NASH患者肠道中氨基酸、碳水化合物、多聚糖、脂质、辅酶因子和维他命代谢相关基因表达显著减少。2.与HC和NAFL组相比较,NASH患者粪便和血清中初级胆汁酸(胆酸和鹅去氧胆酸)水平显著增高(P0.05),次级胆汁酸(脱氧胆酸和石胆酸)在NASH患者中有降低的趋势。另外,血清缬氨酸、丙氨酸、酪氨酸和苯基丙氨酸水平在NAFLD患者中显著增高(P0.05),并且随着疾病进展逐渐增高。3.肠道差异菌与粪便胆汁酸、血清氨基酸水平以及肝脏生化指标之间存在显著相关性,提示IM可能通过改变机体胆汁酸和氨基酸代谢来影响NAFLD的疾病进展;并且血清缬氨酸、丙氨酸、酪氨酸和苯基丙氨酸组合可用于NAFL与NASH的鉴别诊断(AUC=0.863)。结论NAFLD尤其是NASH患者肠道菌群结构及功能发生显著改变,失衡的肠道微生态影响机体肠道中初级胆汁酸向次级转化这一过程,因此,NASH患者粪便中初级胆汁酸显著增高,而次级胆汁酸水平降低,从而影响NAFLD的疾病过程。肠道微生态失衡还可能引起机体氨基酸代谢异常;血清氨基酸水平检测可为鉴别诊断NAFL与NASH提供新方法。
[Abstract]:Background with the globalization of obesity and its associated metabolic syndrome, (NAFLD) has become a chronic liver disease threatening human health worldwide. There is more and more evidence that intestinal (IM) disorder plays an important role in the occurrence and development of NAFLD. However, there is a limited number of relevant studies, especially in the population, and there are no reports on how the dysbacteriosis affects the metabolism of the body. Liver is an important organ involved in metabolism. Bile acid and amino acid metabolism are two main metabolic pathways of liver and are related to the occurrence and development of NAFLD. Our preliminary study showed that IM significantly affected the metabolic phenotype of the host in patients with NAFLD, and initially found abnormal metabolism of bile acids and amino acids. Therefore, this study will further explore the relationship between bile acid, amino acid metabolism and IM and its role in the development of NAFLD. Methods in this study, (NAFL), patients with non-alcoholic fatty liver and healthy individuals with (HC) were selected as subjects, and the structure and function of intestinal microflora in NAFLD patients were studied by molecular ecology method. High performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and nuclear magnetic detection (NMR) were used to detect the changes of small molecule metabolic spectrum in patients with NAFLD, especially the serum and fecal bile acids and serum amino acids. To explore the potential association between changes of IM and changes of bile acid and amino acid metabolism by statistical analysis of biological information. Results 1. The results of microflora analysis showed that the structure and function of IM in NASH patients were significantly different from those in NAFL and HC groups. The intestinal microflora biodiversity in NASH group was significantly lower than that in NAFL and HC groups. In NASH patients, Bacteroides significantly decreased, while Proteus and Actinomycetes increased significantly. In the family level, Bacteroides decreased in the intestinal tract of the NASH group, but increased significantly in the Enterobacteriaceae group. At the generic level, the Bacteroides decreased significantly in the intestinal tract of NASH patients, while the Blautia genus increased significantly. Changes and bile acids in Bacteroides, Enterobacteriaceae and Blautia genera. Metabolic abnormalities are closely related. The expression of amino acids, carbohydrates, polysaccharides, lipids, coenzyme factors and vitamin metabolism-related genes in the intestine of patients with NASH was significantly decreased by functional metabolism analysis. Compared with HC and NAFL groups, the levels of primary bile acids (cholic acid and chenodeoxycholic acid) in feces and serum of NASH patients were significantly increased (P0.05), and secondary bile acids (deoxycholic acid and lithocholic acid) tended to decrease in NASH patients. In addition, the serum levels of valine, alanine, tyrosine and phenylalanine were significantly increased in NAFLD patients (P0.05), and gradually increased with the disease progression. There is a significant correlation between intestinal bacteria and fecal bile acid, serum amino acid level and liver biochemical index, suggesting that IM may affect the disease progression of NAFLD by changing the metabolism of bile acid and amino acid. The combination of valine, alanine, tyrosine and phenylalanine can be used in differential diagnosis of NAFL and NASH (AUC=0.863). Conclusion the structure and function of intestinal flora in patients with NAFLD, especially in patients with NASH, are significantly changed. The imbalance of intestinal microecology affects the process of primary bile acid transformation from primary bile acid to secondary bile acid in intestinal tract. Therefore, the fecal primary bile acid in NASH patients is significantly increased. The level of secondary bile acids decreased, thus affecting the disease process of NAFLD. The imbalance of intestinal microecology may also lead to abnormal metabolism of amino acids, and the detection of serum amino acids may provide a new method for differential diagnosis of NAFL and NASH.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R575.5

【相似文献】