The liver cirrhosis reduced Tdo2, indoleamine‐2,3‐dioxygenase 1 (Ido2) and kynurenine 3‐monooxygenase (Kmo) mRNA levels in the liver (Figure 2D), as well as liver NAD+, plasma NAM and intestinal NAD+ levels in mice (Figure 2E; Figure S2F, Supporting Information). This evidence concerns the gene TDO2 and cirrhosis of liver.