The kidneys play an integral role in the metabolism of TRP.13 The rate-limiting enzyme IDO1 is overexpressed in kidney tissues.14 Interestingly, aberrations in TRP metabolism and specific enzyme activities in the KYN pathway could contribute to the pathogenesis of T2D.15 It should be emphasized that the molecular mechanisms of inflammatory pathways are also different in nondiabetic vs diabetic CKD,16 the latter group having an accelerated loss of kidney function than the former.17 Therefore, TRP metabolism may have potentially important clinical implications to CKD secondary to T2D. Here, IDO1 is linked to chronic kidney disease.