Taken together with other published studies, Arinze’s study shows that activation of AhR by IS and other tryptophan metabolites is now implicated in multiple pathophysiologic processes associated with CKD, including glomerular injury, renal fibrosis, atherogenesis and cardiovascular disease, protein energy wasting, renal anemia, loss of bone mineralization, and cognitive dysfunction (5). The gene discussed is AHR; the disease is renal fibrosis.