Indoxyl sulfate-lowering capacity of oral sorbents affects the prognosis of kidney function and oxidative stress in chronic kidney disease.

OBJECTIVES: Indoxyl sulfate shows nephrotoxicity and is a stimulating factor for progression of chronic kidney disease (CKD). This study was conducted to determine (1) whether the indoxyl sulfate-lowering capacity of oral sorbents (Kremezin [AST-120], Kureha Corporation, Tokyo, Japan; Merckmezin, Merck Hoei Ltd., Osaka, Japan) affects the prognosis of kidney function in CKD, and (2) whether oral sorbents reduce the markers of oxidative stress.

METHODS: Rats with CKD were produced by 4/5 nephrectomy and were randomized into 3 groups: control rats, Merckmezin-treated rats, and Kremezin-treated rats. Kremezin and Merckmezin were administered to rats at a dose of 4 g/kg with powder chow for 16 weeks, whereas powder chow alone was administered to control rats.

RESULTS: Administration of Kremezin significantly decreased serum and urine levels of indoxyl sulfate and serum creatinine and significantly increased creatinine clearance as compared with control values. The change in serum indoxyl sulfate noted from the initial to the final week showed a positive correlation with the change in serum creatinine and a negative correlation with the change in creatinine clearance. Kremezin significantly reduced urine levels of acrolein, a marker of oxidative stress, as compared with control levels.

CONCLUSIONS: The indoxyl sulfate-lowering capacity of oral adsorbents affects the prognosis of kidney function in CKD. The more serum indoxyl sulfate is reduced, the better kidney function is preserved. Kremezin alleviates oxidative stress in the kidneys by reducing serum levels of indoxyl sulfate.