The importance of the gut microbiota after bariatric surgery. Aron-Wisnewsky Judith,Doré Joel,Clement Karine Nature reviews. Gastroenterology & hepatology The gut microbiota is recognized to have an important role in energy storage and the subsequent development of obesity. To date, bariatric surgery (indicated for severe obesity) represents the only treatment that enables substantial and sustained weight loss. Bariatric surgery is also a good model to study not only the pathophysiology of obesity and its related diseases but also the mechanisms involved in their improvement after weight reduction. Scarce data from humans and animal models have demonstrated that gut microbiota composition is modified after Roux-en-Y gastric bypass (RYGB), suggesting that weight reduction could affect gut microbiota composition. However, weight loss might not be the only factor responsible for those modifications. Indeed, bariatric surgery not only improves hormonal and inflammatory status, but also induces numerous changes in the digestive tract that might account for the observed modifications of microbiota ecology. In future bariatric surgery studies in humans or mice, these major surgery-induced modifications will need to be taken into account when analyzing the link between gut microbiota composition, obesity, its complications and their improvement after bariatric surgery. This Review outlines the potential mechanisms by which the major changes in the digestive tract after bariatric surgery can affect the gut microbiota. 10.1038/nrgastro.2012.161

Gut microbiome and serum metabolome alterations in obesity and after weight-loss intervention. Liu Ruixin,Hong Jie,Xu Xiaoqiang,Feng Qiang,Zhang Dongya,Gu Yanyun,Shi Juan,Zhao Shaoqian,Liu Wen,Wang Xiaokai,Xia Huihua,Liu Zhipeng,Cui Bin,Liang Peiwen,Xi Liuqing,Jin Jiabin,Ying Xiayang,Wang Xiaolin,Zhao Xinjie,Li Wanyu,Jia Huijue,Lan Zhou,Li Fengyu,Wang Rui,Sun Yingkai,Yang Minglan,Shen Yuxin,Jie Zhuye,Li Junhua,Chen Xiaomin,Zhong Huanzi,Xie Hailiang,Zhang Yifei,Gu Weiqiong,Deng Xiaxing,Shen Baiyong,Xu Xun,Yang Huanming,Xu Guowang,Bi Yufang,Lai Shenghan,Wang Jian,Qi Lu,Madsen Lise,Wang Jiqiu,Ning Guang,Kristiansen Karsten,Wang Weiqing Nature medicine Emerging evidence has linked the gut microbiome to human obesity. We performed a metagenome-wide association study and serum metabolomics profiling in a cohort of lean and obese, young, Chinese individuals. We identified obesity-associated gut microbial species linked to changes in circulating metabolites. The abundance of Bacteroides thetaiotaomicron, a glutamate-fermenting commensal, was markedly decreased in obese individuals and was inversely correlated with serum glutamate concentration. Consistently, gavage with B. thetaiotaomicron reduced plasma glutamate concentration and alleviated diet-induced body-weight gain and adiposity in mice. Furthermore, weight-loss intervention by bariatric surgery partially reversed obesity-associated microbial and metabolic alterations in obese individuals, including the decreased abundance of B. thetaiotaomicron and the elevated serum glutamate concentration. Our findings identify previously unknown links between intestinal microbiota alterations, circulating amino acids and obesity, suggesting that it may be possible to intervene in obesity by targeting the gut microbiota. 10.1038/nm.4358