Levels of Indoxyl Sulfate in Kidney Transplant Patients, and the Relationship With Hard Outcomes

Background: Indoxyl sulfate (IS) is a protein-bound uremic toxin that is known to be associated with the risk of cardiovascular (CV) disease and death in both predialysis and dialysis patients. Data on levels of protein-bound uremic toxins in kidney transplant patients are scarce. The study's objective was to evaluate the levels of IS in kidney transplant patients and the relationship with hard outcomes. Methods and Results: In 311 kidney transplant patients, IS levels were measured immediately before transplantation (T0), and 1 month (M1) and 12 months (M12) afterwards. Over a mean +/- standard deviation follow-up period of 113+/-29 months, a total of 55 deaths, 70 CV events and 71 graft losses were recorded. We observed a rapid significant decrease (below or near the normal value) in IS levels after kidney transplantation. Total and free IS levels at M12 were significantly higher in non-transplant patients than in transplant patients (P=0.003 and <0.0001 respectively), despite having similar estimated glomerular filtration rates. Lastly, IS levels were not associated with overall mortality, CV events or graft loss at T0, M1 or M12. Conclusions: IS levels were significantly lower in kidney transplant receipts than in non-recipients suggesting that kidney transplantation protects against an increase in IS levels. IS levels were not associated with hard outcomes in kidney transplant patients.