Supplementary Material for: Dietary Protein and Fiber Affect Gut Microbiome and Treg/Th17 Commitment in Chronic Kidney Disease Mice

<b><i>Background:</i></b> Patients with chronic kidney disease (CKD) have dysbiosis, dysmetabolism, and immune dysregulation. Gut microbiome plays an important role shaping the immune system which is an important modulator of CKD progression. <b><i>Methods:</i></b> We compared the effect of a diet low in protein and high in fiber (LP-HF; <i>n</i> = 7) to that of diet rich in protein, but low in fiber (HP-LF; <i>n</i> = 7) on gut microbiome and T-cell commitment in male CKD (Alb/TGF-β1) mice. The gut microbiomes of these mice were subjected to 16S rRNA taxonomic profiling at baseline, 6 weeks and 12 weeks of the study. <b><i>Results:</i></b> The LP-HF diet was associated with an increase in <i>Butyricicoccus pullicaecorum</i> BT, a taxon whose functions include those closely related to butyric acid synthesis (Kendall’s W statistic = 180 in analysis of microbiome composition). HP-LF diet was associated with increased abundance of two predominantly proteolytic bacterial strains related to <i>Parabacteroides distasonis</i> (W statistic = 173), <i>Mucispirillum schaedleri</i>, and <i>Bacteroides dorei</i> (W statistic = 192). Pathway analysis suggested that the LP-HF diet induced carbohydrate, lipid, and butyrate metabolism. As compared with HP-LF mice, LP-HF mice had 1.7-fold increase in CD4+Foxp3+Treg cells in spleen and 2.4-fold increase of these cells in peripheral blood. There was an 87% decrease in percentage of CD4+ Th17 + cells in spleen and an 85% decrease in peripheral blood, respectively, in LP-HF mice compared to the HP-LF mice. <b><i>Conclusion:</i></b> The LP-HF diet promotes the proliferation of saccharolytic bacteria and favors T-cell commitment toward Treg cells in a CKD mouse of model. Clinical significance of the finding needs to be further investigated.<b><i>背景：</i></b> 慢性肾脏病（CKD）患者存在菌群失调、代谢紊乱及免疫功能失调。肠道菌群（gut microbiome）在塑造免疫系统中发挥关键作用，而免疫系统亦是慢性肾脏病进展的重要调节因素。<b><i>方法：</i></b> 本研究对比了低蛋白高纤维（LP-HF；n=7）与高蛋白低纤维（HP-LF；n=7）两种饮食对雄性慢性肾脏病（Alb/TGF-β1）小鼠肠道菌群及T细胞定向分化的影响。本研究分别在实验基线、第6周及第12周，对这些小鼠的肠道菌群进行16S rRNA分类学测序分析。<b><i>结果：</i></b> 低蛋白高纤维饮食可显著富集布特林氏球菌（Butyricicoccus pullicaecorum BT），该类群的功能与丁酸合成密切相关（菌群组成分析中肯德尔W统计量=180）。高蛋白低纤维饮食则使与副杆菌（Parabacteroides distasonis，W统计量=173）、沙德勒氏粘螺菌（Mucispirillum schaedleri）及多雷拟杆菌（Bacteroides dorei，W统计量=192）相关的两种主要蛋白水解类细菌丰度升高。通路分析显示，低蛋白高纤维饮食可激活碳水化合物、脂质及丁酸代谢通路。与高蛋白低纤维饮食组小鼠相比，低蛋白高纤维饮食组小鼠脾脏中CD4+Foxp3+调节性T细胞（Treg）数量升高1.7倍，外周血中该类细胞数量升高2.4倍。相较于高蛋白低纤维饮食组，低蛋白高纤维饮食组小鼠脾脏中CD4+辅助性T细胞17（Th17）占比降低87%，外周血中该类细胞占比降低85%。<b><i>结论：</i></b> 在慢性肾脏病小鼠模型中，低蛋白高纤维饮食可促进糖解类细菌增殖，并推动T细胞向调节性T细胞分化。该发现的临床意义仍需进一步研究阐明。