TPH1 and chronic kidney disease: In addition, Chen et al. found that five metabolites, including 5-methoxytryptophan (5-MTP), canavaninosuccinate (CSA), acetylcarnitine, tiglylcarnitine, and taurine, can be used to accurately identify the clinical stages of CKD, and that tryptophan hydroxylase-1 (TPH-1) presents a potential therapeutic target in CKD (Chen et al., 2019b).