Lobel et al. (2020) found that a high sulfur amino acid-containing diet modulated the production of indole and IS via sulfide inhibition of tryptophanase (TnaA), thus abrogating uremic toxicity and ameliorating kidney function in CKD mice. Therefore, high sulfur amino acid diet can improve gut microbiota through posttranslational modification without altering the composition of microbial community (Lobel et al., 2020). This evidence concerns the gene TDO2 and chronic kidney disease.