GCG and type 2 diabetes mellitus: To answer this, we divided 40 type 2 diabetes patients in the vildagliptin group (who had pre- and post-treatment metagenomes and fasting GLP-1 values) into two subgroups according to their GLP-1 responses (see Methods), namely the high response (HR, n=20, PC%>50.18%) and low response (LR, n=20, PC%≤50.18%) groups (Fig. 4a).