Fig. 6

Arginine and polyamine metabolism after 2-day drug treatment. Pathway of arginine metabolism toward polyamine biosynthesis and metabolism in A) serum and E) gut lumen, and C) pathway of arginine metabolized to nitric oxide synthesis. Illustration adapted from KEGG histidine metabolism pathway (map00330) [45]. Metabolite conversion ratio plot in B) spermidine to 4-acetamidobutanoid acid in serum, putrescine to arginine in both D) lumen and F) serum in the four 2-day treatment groups of tacrolimus, antibiotics, tacrolimus and antibiotics together, and no treatment control. Y axis represents the ratios normalized level between the indicated metabolites. The ROC curve used to calculate area under curve (AUC) as a metric quantifying the overall ability of the metabolite to correctly classify the experimental conditions. Closest to top-left core of ROC (red dot) as the optimal cutoff value, shown in bargraph (red line). P value was calculated using 2-sample t-tests between tacrolimus and control groups and displayed atop the boxplots. Black points representing mice, horizontal line representing mean, yellow dots presenting median, the top and bottom of the box are the lower and upper quartile. Abbreviations: ADMA: asymmetric dimethylarginine; SDMA: symmetric dimethylarginine; SAM: S-adenosylmethionine