A nexus of progression of chronic kidney disease: charcoal, tryptophan and profibrotic cytokines.

Fibrosis plays a role in the pathogenesis of progressive chronic kidney disease (CKD). The inhibition of the renin-angiotensin system, which promotes fibrosis, has become the standard of care in the treatment of patients with CKD. A novel charcoal compound, AST-120, has been used for over a decade in Japan to prevent progression of CKD. It is thought that the oral administration of AST-120 blocks the intestinal absorption of tryptophan-derived indole. This prevents the hepatic conversion of indole to indoxyl sulfate (IS). IS has been shown to stimulate the production of profibrotic cytokines such as transforming growth factor-beta. AST-120 lowers IS in a dose dependent fashion and does not change the creatinine appearance rate in the urine. Enteric capsules containing Bifidobacterium longum have been shown to prevent progression of CKD in a preliminary study. These findings suggest that prospective clinical trials be undertaken to determine if these other potential methods of inhibiting fibrosis are useful in slowing progressive CKD.