Sci Transl Med：胃分流术或可改变肠道微生物

刊登在国际杂志Sci Transl Med上的一篇在小鼠中进行的一项新的研究报道中指出，胃分流术会改变肠道的微生物构成，而这些变化可能是手术后病人体重快速下降的原因。探索胃分流术后造成体重丧失的基础机制可能会帮助研究人员找出替代该手术的非外科疗法。Alice Liou及其同事观察到在手术后人类及大鼠肠道中2组微生物丰度的改变，即像大肠杆菌这样的变形杆菌及疣微菌目的改变。这些细菌在正常人和啮齿动物中通常有着相对较低的水平。

研究人员对手术会如此快而且强力地改变肠道微生物（这些变化仅在手术后1周就被观察到）以及这些效应在小鼠、大鼠及人类中如此一致地出现而感到惊奇。微生物群落的改变出现在整个胃肠道，特别是会在远离手术位置的远端肠道中出现。此外，在无菌小鼠体内植入从那些接受过手术的动物体内获取的微生物会使这些无菌小鼠的体重下降且脂肪组织减少。

文章的作者并不完全知道为什么这些肠道微生物的变化会促使体重下降，但一个可能的机制也许是手术后小鼠体内产生的短链脂肪酸类型发生了变化。这些结果表明，肠道菌群的改变不是由体重减轻或热卡受限引起的，而是由胃分流术本身所引起的独特变化造成的。

doi:10.1126/scitranslmed.3005687
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Conserved Shifts in the Gut Microbiota Due to Gastric Bypass Reduce Host Weight and Adiposity

Alice P. Liou1, Melissa Paziuk1, Jesus-Mario Luevano Jr.2, Sriram Machineni1, Peter J. Turnbaugh2,* and Lee M. Kaplan1,*

Roux-en-Y gastric bypass (RYGB) results in rapid weight loss, reduced adiposity, and improved glucose metabolism. These effects are not simply attributable to decreased caloric intake or absorption, but the mechanisms linking rearrangement of the gastrointestinal tract to these metabolic outcomes are largely unknown. Studies in humans and rats have shown that RYGB restructures the gut microbiota, prompting the hypothesis that some of the effects of RYGB are caused by altered host-microbial interactions. To test this hypothesis, we used a mouse model of RYGB that recapitulates many of the metabolic outcomes in humans. 16S ribosomal RNA gene sequencing of murine fecal samples collected after RYGB surgery, sham surgery, or sham surgery coupled to caloric restriction revealed that alterations to the gut microbiota after RYGB are conserved among humans, rats, and mice, resulting in a rapid and sustained increase in the relative abundance of Gammaproteobacteria (Escherichia) and Verrucomicrobia (Akkermansia). These changes were independent of weight change and caloric restriction, were detectable throughout the length of the gastrointestinal tract, and were most evident in the distal gut, downstream of the surgical manipulation site. Transfer of the gut microbiota from RYGB-treated mice to nonoperated, germ-free mice resulted in weight loss and decreased fat mass in the recipient animals relative to recipients of microbiota induced by sham surgery, potentially due to altered microbial production of short-chain fatty acids. These findings provide the first empirical support for the claim that changes in the gut microbiota contribute to reduced host weight and adiposity after RYGB surgery.

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