It has been suggested that trimethylamine N‐oxide (TMAO) is associated with increased risk of diabetes and cardiovascular disease (CVD) morbidity and mortality. However, it is not known whether increased TMAO concentrations is associated with obesity. In the current study, we summarized the evidence related to the association of circulating TMAO with the risk of obesity measurements, including body mass index (BMI), waist circumference (WC), and waist‐to‐hip ratio (WHR) in a two‐class and dose‐response meta‐analysis of observational studies. A systematic search carried out in PubMed, SCOPUS, Cochrane, and ProQuest through September 30, 2019 resulted in 12 eligible studies which were included in the current meta‐synthesis. In these studies, BMI was reported but there were no reports of WC or WHR. Meta‐analysis of two‐class variables and dose‐response meta‐analysis of continuous variables were performed. Subgroup analysis and meta‐regression were also performed to identify the source of heterogeneity. There was a dose‐response association between circulating TMAO concentration and increased BMI in studies involving healthy individuals (P nonlinearity = .007), while no evidence of departure from linearity was observed according to study design or among patients with CVD. Results showed the highest category of TMAO was associated with 0.56 kg/m² increase in BMI (weighted mean difference [WMD], 0.563; CI, 0.026‐1.100; P = .04). The results of the current meta‐analysis revealed a positive association between circulating TMAO and obesity as presented by increased BMI. Moreover, a dose‐dependent association between circulating TMAO and obesity was also identified in apparently healthy individuals. This is the first meta‐analysis to reveal positive dose‐dependent associations between circulating TMAO concentration and obesity.

中文翻译：

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肠道菌群衍生的代谢物三甲胺N-氧化物（TMAO）可能增加成人肥胖的风险：一项探索性的系统综述和剂量反应荟萃分析。

有人提出，三甲胺N-氧化物（TMAO）与糖尿病和心血管疾病（CVD）的发病率和死亡率增加的风险有关。但是，尚不知道增加的TMAO浓度是否与肥胖有关。在本研究中，我们总结了与循环TMAO与肥胖测量风险相关的证据，包括体重指数（BMI），腰围（WC）和腰臀比（WHR）两者观察性研究的分类和剂量反应荟萃分析。截至2019年9月30日，在PubMed，SCOPUS，Cochrane和ProQuest中进行的系统搜索导致12项符合条件的研究被纳入当前的元合成中。在这些研究中，有BMI的报道，但没有WC或WHR的报道。进行了两类变量的荟萃分析和连续变量的剂量反应荟萃分析。还进行了亚组分析和荟萃回归，以确定异质性的来源。在涉及健康个体的研究中，循环TMAO浓度与BMI升高之间存在剂量反应关系（P非线性= .007），而根据研究设计或在CVD患者中未观察到偏离线性的证据。结果显示，TMAO的最高类别与BMI升高0.56 kg / m ^2有关（加权平均差异[WMD]为0.563； CI为0.026-1.100；P = .04）。当前的荟萃分析结果显示，BMI升高提示循环中的TMAO与肥胖之间存在正相关。此外，在显然健康的个体中，还发现了循环TMAO与肥胖之间的剂量依赖性关系。这是首次揭示循环TMAO浓度与肥胖之间呈剂量依赖性正相关的荟萃分析。