Effects of N-acetyl-L-tryptophan on desorption of the protein-bound uremic toxin indoxyl sulfate and effects on uremic sarcopenia

Introduction: Indoxyl sulfate (IS) is a protein-bound uremic toxin that causes uremic sarcopenia. IS has poor dialysis clearance; however, the addition of a binding competitor improves its removal efficiency. Methods: Dialysis experiments were performed using N-acetyl-l-tryptophan (L-NAT) instead of l-tryptophan (Trp) using pooled sera obtained from dialysis patients. The molecular structures of L-NAT and Trp were similar to that of IS. Therefore, we examined whether Trp and L-NAT were involved in muscle atrophy in the same manner as IS by performing culture experiments using a human myotube cell line. Results: The removal efficiency of L-NAT was the same as that of Trp. However, L-NAT concentrations in the pooled sera increased at the end of the experiment. Trp (1 mM) decreased the area of human myocytes, similar to IS, whereas L-NAT did not. Conclusion: L-NAT is a binding competitor with the ability to remove protein-bound IS while preventing sarcopenia.