Our genetic makeup influences whether we are fat or thin by shaping which types of microbes thrive in our body, according to a study by researchers at King's College London and Cornell University.
By studying pairs of twins at King's Department of Twin Research, researchers identified a specific, little known bacterial family that is highly heritable and more common in individuals with low body weight. This microbe also protected against weight gain when transplanted into mice.
The results, published today in the journal Cell, could pave the way for personalised probiotic therapies that are optimised to reduce the risk of obesity-related diseases based on an individual's genetic make-up.
Previous research has linked both genetic variation and the composition of gut microbes to metabolic disease and obesity. Despite these shared effects, the relationship between human genetic variation and the diversity of gut microbes was presumed to be negligible.
In the study, funded by National Institutes of Health (NIH), researchers sequenced the genes of microbes found in more than 1,000 fecal samples from 416 pairs of twins. The abundances of specific types of microbes were found to be more similar in identical twins, who share 100 per cent of their genes, than in non-identical twins, who share on average only half of the genes that vary between people. These findings demonstrate that genes influence the composition of gut microbes.
The type of bacteria whose abundance was most heavily influenced by host genetics was a recently identified family called 'Christensenellaceae'. Members of this health-promoting bacterial family were more abundant in individuals with a low body weight than in obese individuals. Moreover, mice that were treated with this microbe gained less weight than untreated mice, suggesting that increasing the amounts of this microbe may help to prevent or reduce obesity.
Professor Tim Spector, Head of the Department of Twin Research and Genetic Epidemiology at King's College London, said: 'Our findings show that specific groups of microbes living in our gut could be protective against obesity -- and that their abundance is influenced by our genes. The human microbiome represents an exciting new target for dietary changes and treatments aimed at combating obesity.
'Twins have been incredibly valuable in uncovering these links -- but we now want to promote the use of microbiome testing more widely in the UK through the British Gut Project. This is a crowd-sourcing experiment that allows anyone with an interest in their diet and health to have their personal microbes tested genetically using a simple postal kit and a small donation via our website (www.britishgut.org). We want thousands to join up so we can continue to make major discoveries about the links between our gut and our health.'
Ruth Ley, Associate Professor at Cornell University in the United States, said: 'Up until now, variation in the abundances of gut microbes has been explained by diet, the environment, lifestyle, and health. This is the first study to firmly establish that certain types of gut microbes are heritable -- that their variation across a population is in part due to host genotype variation, not just environmental influences. These results will also help us find new predictors of disease and aid prevention.'

参考译文：

肠道菌群研究越来越受到重视，已经有研究证据提示肠道细菌是人体不可或缺的一部分。

以往的研究也已发现宿主遗传变异和肠道菌群组成与代谢性疾病和肥胖之间存在相关性。但是，人类遗传变异和肠道菌群多样性之间的关系仍被假定为可忽略不计。

10月6日发表在CELL杂志上的一项研究显示，一个肠道菌家族具有高度遗传性，更常见于瘦人。将其移植进小鼠肠道可以防止实验鼠体重增加。

由NIH资助的这项研究中，来自伦敦大学国王大学和康奈尔大学的研究人员对取自416对双胞胎的超过1000份粪便样品中微生物基因进行测序发现，与仅有一半基因相同的异卵双胞胎比较，具有完全相同基因的同卵双胞胎肠道某种特定微生物的相对含量更相似。结果表明，遗传因素对于肠道群种类的影响大于环境因素。

这个相对含量极大程度上受宿主遗传影响的肠道益生菌家族被命名为“Christensenellaceae”。这个益生菌家族成员菌被发现在瘦人肠道丰度高于肥胖人群。而且，接受这类细菌移植的小鼠不容易长胖，说明增加肠道中这类细菌的量可能有助于防止或减轻肥胖。

本研究的意义在于： 1）第一次确立了宿主遗传因素决定肠道细菌种类的相对含量； 2）证明多种可遗传菌种可共存共现； 3）最受遗传影响的Christensenellaceae益生菌与宿主体重指数相关； 4）预示着将来可以通过“粪便移植”帮助防治肥胖和肥胖相关疾病。