There is a recent growing evidence that abnormalities in the microbiota composition can have a major role in the development of obesity and diabetes and that some actions of metformin may be mediated by gut bacteria. Several mechanisms have been found. A reduced microbial diversity is associated to inflammation, insulin-resistance, and adiposity. In particular, a rise in the Firmicutes/Bacteroidetes ratio is related to a low-grade inflammation and to an increased capability of harvesting energy from food. Interestingly, high-fat-diet favors the growth of bacteria capable of extracting more energy from food. Changes in some metabolites, such as short-chain fatty acids (SCFAs), produced by gut microbiota, and decreased amounts of the Akkermansia muciniphila are associated with the presence of type 2 diabetes. Among the mechanisms by which metformin acts on glucose metabolism and on the cardiovascular risk, some of them are due to positive effects on gut microbiota. A shift toward positive SCFAs produced by bacteria, an increase in some bacterial strains, including A. muciniphila, and some actions on bile acids mediated by microbiota have been described. All these recent advances have been reported and discussed.

最近有越来越多的证据表明，微生物群组成的异常可能在肥胖症和糖尿病的发展中起主要作用，二甲双胍的某些作用可能是由肠道细菌介导的。已经发现了几种机制。减少的微生物多样性与炎症，胰岛素抵抗和肥胖有关。特别是，硬顶菌/拟杆菌比的升高与轻度发炎以及从食物中获取能量的能力增强有关。有趣的是，高脂饮食有利于细菌的生长，这种细菌能够从食物中提取更多的能量。肠道菌群产生的某些代谢物（例如短链脂肪酸（SCFA））的变化以及黏液阿克曼氏菌的减少与2型糖尿病的存在有关。在二甲双胍对葡萄糖代谢和心血管风险起作用的机制中，其中一些归因于对肠道菌群的积极作用。已经描述了由细菌向阳性SCFA的转变，包括粘液曲霉在内的某些细菌菌株的增加以及由微生物群介导的对胆汁酸的某些作用。所有这些最近的进展都得到了报道和讨论。