Supplementary Material for: Role of pre-surgical gut microbial diversity in Roux-en-Y gastric bypass weight-loss response: A cohort study

Introduction: Roux-en-Y gastric bypass substantially alters the gut microbial composition which could be associated with the metabolic improvements seen after surgery. Few studies have been conducted in Latin American populations, such as Mexico where obesity prevalence is above 30% in the adult population. Thus, the aim of this study was to characterize the changes in gut microbiota structure in a Mexican cohort before and after Roux-en-Y gastric bypass and to explore whether surgery-related changes in the microbial community were associated with weight loss.
Methods: Biological samples from patients who underwent Roux-en-Y gastric bypass were examined before and 12 months after surgery. Fecal microbiota characterization was performed through 16S rRNA sequencing.
Results: Twenty patients who underwent Roux-en-Y gastric bypass showed a median excess weight loss of 66.8% 12 months after surgery. Surgery increased alpha diversity estimates (Chao, Shannon index and observed operational taxonomic units (OTUs), p<0.05), and significantly altered gut microbiota composition. Abundance of four genera were significantly increased after surgery: Oscillospira, Veillonella, Streptococcus, and an unclassified genus from Enterobacteriaceae family (PFDR<0.1). The change in Veillonella abundance was associated with lower excess weight loss (rho=-0.446, p=0.063) and its abundance post-surgery with a greater BMI (rho=0.732, P=5.4x10-4). In subjects without type 2 diabetes lower bacterial richness and diversity before surgery were associated with a greater Veillonella increase after surgery (p<0.05), suggesting that a lower bacterial richness before surgery could favor the bloom of certain oral-derived bacteria that could negatively impact weight loss.
Conclusion: Pre-surgical microbiota profile may favor certain bacterial changes associated with less successful results.

引言：Roux-en-Y胃旁路术（Roux-en-Y gastric bypass）可显著改变肠道微生物组组成，这或与术后出现的代谢改善相关。目前针对拉丁美洲人群（如成人肥胖患病率超过30%的墨西哥）的相关研究较少。因此，本研究旨在明确墨西哥队列人群接受Roux-en-Y胃旁路术前后的肠道菌群结构变化，并探讨菌群群落的手术相关变化是否与体重减轻相关。

方法：对接受Roux-en-Y胃旁路术的患者，分别在术前及术后12个月采集其生物样本，并通过16S rRNA测序（16S rRNA sequencing）对粪便菌群进行表征分析。

结果：20例接受Roux-en-Y胃旁路术的患者，术后12个月的中位多余体重丢失率为66.8%。手术可提升肠道菌群α多样性（包括Chao1指数、Shannon指数及观测到的操作分类单元（OTUs），p<0.05），并显著改变肠道微生物组组成。术后有4个菌属的丰度显著升高：Oscillospira、Veillonella、Streptococcus，以及肠杆菌科（Enterobacteriaceae）的1个未分类菌属（假发现率校正后P<0.1，PFDR<0.1）。Veillonella丰度的变化与更低的多余体重丢失率相关（rho=-0.446，p=0.063），而术后其丰度与更高的体质量指数（BMI）相关（rho=0.732，P=5.4×10^-4）。在无2型糖尿病的受试者中，术前较低的菌群丰富度与多样性与术后Veillonella的更大幅度升高相关（p<0.05），这提示术前较低的菌群丰富度或有利于某些源自口腔的细菌增殖，进而对体重减轻产生负面影响。

结论：术前菌群特征或会促使某些细菌群落发生变化，进而与较差的手术预后相关。