Nature子刊：肠道菌群与肺部疾病的关系

肠肺相连，还是肺与肠道相表里？目前看来，至少它们的细菌和免疫功能是相通的。

A curious connection: Teasing apart the link between gut microbes and lung disease

Nature Medicine

DOI: 10.1038/nm0417-402

论文摘要

One morning last autumn, Robert Dickson inserted a long, thin tube fitted with a miniscule camera down the windpipe of a healthy volunteer. The volunteer was slightly sedated—enough not to mind a tube down his throat, but awake enough to heed instructions to cough. As the bronchoscope made its way down, Dickson followed the images on a screen next to him, which showed the trachea and its cartilaginous arches that resemble the rib vaults of some cathedral ceilings. He then guided the bronchoscope to the spot where the trachea branches into the two lungs and inserted a long filament, armed with a small brush at its tip, down the scope. The brush then picked up a sample of the microbes that inhabit this section of the airway, after which Dickson pulled the entire apparatus back up. 

This procedure is something that Dickson and his collaborators routinely do to determine the composition of bacterial colonies in the lung. By detailing the microbial makeup within the lungs of healthy volunteers, he hopes to strike upon insights that can help to inform the treatment of various lung ailments. Dickson, a pulmonary and critical-care physician at the University of Michigan in Ann Arbor, primarily treats patients who develop lung infections such as pneumonia, often as a result of extended stays in intensive care units (ICUs). These patients tend to be among the sickest and have weaker immune systems, and prolonged hospital stays make them more susceptible to acquiring infections from the hospital environment. Dickson uses the same bronchoscopic technique of brushing the airways for microbes in his healthy volunteers as he does to sample bacteria in his patients to discern, for example, whether a pneumonia infection is caused by Pseudomonas aeruginosa or Streptococcus pneumoniae. Knowing which types of bacteria are present helps him to determine the best course of treatment. 

But Dickson and his colleagues are increasingly realizing that the microbes in the lung don’t seem to be the sole ones contributing to pneumonia. Microbes in the gut also seem to have some influence on lung health. “I think we’ve all been surprised by how strong the connection is between gut bacteria and lung health,” he says. 

At least two recent studies from Dickson’s team support this connection. But researchers still don’t know exactly how the microbes in the gut sway lung health. Some suggest that by-products of digestion influence the body’s immune system, and this, in turn, exerts control on inflammation in the lungs. By contrast, others point to the fact that the gut and lung are both bathed in lymph, and posit that this fluid might act as a transporter of bacteria between the two organs.

实验综述

① 肺部菌群可能不是唯一在肺炎中起作用的菌群，肠道菌群也可能对肺部健康有影响；

② 肠道中的消化副产物可能影响免疫系统从而调控肺部的炎症，而肠道菌群和肺部菌群可能通过淋巴中的液体互相交换；

③ 2015年开始的2项临床试验试图研究，分别通过益生元和抗生素调节肠道菌群，是否能影响肺部健康：

④ 另外一种理论是，肠道菌群直接在呼吸道中繁殖并影响肺部健康；

⑤ 肠-肺轴理论有许多证据支持，已有公司在研究以肠-肺轴作为潜在治疗靶点的可能。