肠道菌群失调在追赶生长导致的代谢综合征中的病因学作用研究

Epidemiological studies showed individuals with low birth-weight and early-life catch-up growth are at high risk of obesity and metabolic syndrome, but the mechanisms remain unclear. Recent studies showed gut microbiota can influence the onset and development of metabolic syndrome. Supported by the previous grant of National Natural Science Foundation of China, we found early-life gut microbiota dysbiosis was associated with the metabolic syndrome in mice with low birth-weight and early-life catch-up growth, and identified the decrease of potentially beneficial gut bacteria including Rikenella, Blautia and Lactobacillus, and increase of potentially harmful bacteria including Enterorhabdus and Helicobacter were correlated with catch-up growth-induced metabolic syndrome. In this project, the scientific question is “how catch-up growth-induced gut microbiota dysbiosis affects the onset and development of metabolic syndrome”. We will transplant the gut microbiota from catch-up growth mice and normal growth mice respectively to two groups of germ-free mice, and compare the adiposity and insulin resistance between two recipient groups; we will isolate the gut bacteria that are correlated with catch-up growth-induced metabolic syndrome, inoculate germfree mice with potentially harmful bacteria, and inoculate SPF catch-up growth mice with potentially beneficial bacteria, in order to screen for the key functional gut bacteria that can cause or improve obesity and insulin resistance, and study the mechanisms using transcriptomic techniques. This work will provide scientific evidence that gut microbiota can be the interventional target to treat/alleviate catch-up growth-induced metabolic syndrome.

出生体重低、生命早期追赶生长的个体是罹患代谢综合征的高危人群，但机理不明。最新研究表明肠道菌群影响代谢综合征的发生发展。在自然基金青年项目支持下，我们通过小鼠模型发现追赶生长使幼年期肠道菌群结构失调，Rikenella、Blautia、Lactobacillus等潜在有益菌的减少和Enterorhabdus、Helicobacter等潜在有害菌的增多与追赶生长导致的代谢综合征显著相关。本项目围绕“追赶生长导致的菌群失调如何影响代谢综合征的发生发展”的科学问题，将追赶生长小鼠和正常小鼠的肠道菌群分别移植到无菌小鼠的肠道中，比较受体小鼠的肥胖和胰岛素抵抗状况；分离与追赶生长引起的代谢综合征相关的细菌，将潜在有害菌接入无菌小鼠，将潜在有益菌灌胃给SPF级追赶生长小鼠，筛选出可以导致/改善代谢综合征的功能细菌，用转录组学方法研究机制，为通过调节肠道菌群来治疗追赶生长引起的代谢综合征提供理论依据。

低出生体重个体追赶生长引起的代谢综合征的重要病因学因子是氧化应激 、低水平系统炎症，母乳是低出生体重新生儿最好的食物，并且富含细菌。本课题从人母乳中分离并筛选能在新生儿肠道内定植、抗氧化、抗炎的有益菌。我们将人母乳灌胃给无菌小鼠，发现母乳中的唾液链球菌Streptococcus salivarius F286、副血链球菌St. parasanguinis F278、表皮葡萄球Staphylococcus epidermidis R42，路邓葡萄球菌S. lugdunensis F270 和S. lugdunensis B51菌株在悉生小鼠肠道内高丰度稳定定植，说明这些母乳链球菌和葡萄球菌菌株能够在婴儿肠道中定植。体外化学检测显示，我们分离的这些母乳链球菌和葡萄球菌菌株的发酵上清和/或菌体可以清除DPPH自由基和/或羟自由基，或具有铁还原能力，因此具有抗氧化能力。St. salivarius F286 和St. parasanguinis F278的菌体细胞诱导人外周血单核细胞（PBMCs）产生大量的免疫激活因子IL-12，显著延长了秀丽隐杆线虫的寿命并提高线虫免疫相关基因的表达；St. salivarius F286 和St. parasanguinis F278的发酵上清促进PBMCs产生大量的抗炎因子IL-10，并对由TNF-α引起的人肠道上皮HT29细胞的炎症有轻度缓解作用；St. salivarius F286发酵上清轻度促进小鼠CD4+T细胞转化为Treg细胞。给新生仔鼠灌胃St. salivarius F286 和St. parasanguinis F278菌体，显著提高了仔鼠回肠组织中Treg（抗炎）、Th1免疫相关基因、及抗菌肽基因RegⅢγ的表达水平。新生小鼠体内实验与体外细胞培养实验说明这两株母乳链球菌对新生儿免疫系统具有激活和抗炎的双重作用。体外HT29细胞培养实验显示母乳S.lugdunensis F270发酵上清和S.lugdunensis B51菌体也有抗炎作用。另外，我们建立了St. parasanguinis特异性的定量PCR方法。以上结果表明，我们分离筛选的母乳链球菌和葡萄球菌菌株有潜力通过降低氧化应激、抗炎而改善追赶生长引起的代谢综合征，为改善低出生体重儿的代谢综合征、调节新生儿免疫和肠道发育的微生态制剂的开发奠定了基础。