title: Serum concentrations of p-cresyl sulfate and indoxyl sulfate, but not inflammatory markers, increase in incident peritoneal dialysis patients in parallel with loss of residual renal function.
abstract: BACKGROUND
  High serum concentrations of the protein-bound uremic retention solutes p-cresyl sulfate (PCS) and indoxyl sulfate (IndS) and inflammation are associated with increased cardiovascular morbidity and mortality in chronic kidney disease. Renal clearance contributes to up to 80% of the total clearance of PCS and IndS in peritoneal dialysis (PD) patients. Cross-sectional studies evaluating the impact of residual renal function (RRF) on serum concentrations of PCS, IndS, and circulating inflammatory markers have yielded conflicting results. ♢
  
  
  METHODS
  To clarify this issue, we carried out a prospective observational cohort study in incident PD patients (n = 35; 19 men; mean age: 55 ± 17 years). Midday blood samples were collected and analyzed for total serum PCS, IndS, C-reactive protein, and high-sensitivity interleukin 6. Peritoneal and renal clearances were calculated from urine and dialysate collections, and RRF was calculated as the mean of renal urea nitrogen and creatinine clearances. Patients were assessed 1, 6, 12, and 24 months after PD start. Differences between time points were analyzed using linear mixed models (LMMs). ♢
  
  
  RESULTS
  Residual renal function declined significantly over time (LMM p < 0.0001). Peritoneal clearances of both toxins tended to increase, but did not compensate for the declining renal clearances. Serum concentrations of PCS and IndS increased significantly over time (LMM p = 0.01; p = 0.0009). In contrast, total mass removal of both toxins remained stable. Circulating inflammatory markers did not change over time. ♢
  
  
  CONCLUSIONS
  Our data indicate that serum concentrations of PCS and IndS, but not inflammatory markers, increase in incident PD patients in parallel with loss of RRF.
authors.affiliation: Nephrology, University Hospitals, Leuven, Belgium.
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Viaene
authors.forename: Björn K I
authors.initials: BK
authors.lastname: Meijers
authors.forename: Bert
authors.initials: B
authors.lastname: Bammens
authors.forename: Yves
authors.initials: Y
authors.lastname: Vanrenterghem
authors.forename: Pieter
authors.initials: P
authors.lastname: Evenepoel
mesh_terms: D015415:Biomarkers / Q000097:blood; D003408:Cresols / Q000097:blood*; D005260:Female; D006801:Humans; D007200:Indican / Q000097:blood*; D007249:Inflammation / Q000097:blood; D007668:Kidney / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D011446:Prospective Studies; D013463:Sulfuric Acid Esters / Q000097:blood*
chemical_list: D015415:Biomarkers; D003408:Cresols; D013463:Sulfuric Acid Esters; C408690:4-cresol sulfate; D007200:Indican
keywords: Indoxyl sulfate; inflammation; p-cresyl sulfate; residual renal function