Hemodialysis Decreases the Concentration of Accumulated Plant Phenols in the Plasma of Patients on Maintenance Dialysis: Influence of Residual Renal Function.

Plant phenols may accumulate in end-stage kidney disease. The effect of hemodialysis on their plasma concentration remains poorly determined. Contingent on concentration, health-promoting or noxious effects occur; therefore, we assessed plasma concentration in hemodialyzed patients. In total, 21 maintenance hemodialyzed patients with diuresis < 500 mL per day (with oliguria), nine hemodialyzed patients with diuresis ≥ 500 mL per day (without oliguria) and 31 healthy volunteers were included. Nine phenolic acids were identified with high-performance liquid chromatography and total polyphenol concentration was determined with the Folin-Ciocalteu method in pre- or post-hemodialysis plasma and pre- or intra-hemodialysis dialysate. The concentration of total polyphenols was 27% higher in pre-hemodialysis plasma than in that of controls (0.95 ± 0.18 mmol/L [P < 0.0001]). The concentration of total polyphenols was higher in patients with oliguria (1.01 ± 0.17) than in those without (0.84 ± 0.13 mmol/L), despite the former having more intense hemodialysis (Kt/V 1.29 ± 0.31 and 0.77 ± 0.25, respectively). Pre-hemodialysis phenolic acid concentration in patients undergoing dialysis exceeded reference values by 3 to 34 times (3-hydroxyphenylacetic acid and vanillic acid, respectively), from 0.69 (dihydrocaffeic acid) to 169.3 μmol/L (hippuric acid). The concentration of six phenolic acids (3-hydroxyhippuric, caffeic, dihydrocaffeic, hippuric, homovanillic, and vanillic acid) was 1.1 (homovanillic) to 11.3 (3-hydroxyhippuric) times higher in patients with oliguria than in those without. 4-hydroxyhippuric acid occurred more in the plasma of patients with oliguria than in those without oliguria. A single hemodialysis session decreased total polyphenol concentration by 16% and phenolic acids from 30% (caffeic) to 58% (vanillic and 3-hydroxyphenylacetic acid) and these compounds appeared in the dialysate. The percentage decrease (Δ%) of creatinine concentration correlated with the Δ% of total polyphenols and five phenolic acids (3-hydroxyphenylacetic, dihydrocaffeic, hippuric, homovanillic, and vanillic acid). Urea Δ% and Kt/V correlated only with the Δ% of homovanilic acid. The results demonstrate that phenols accumulate variably in hemodialyzed patients and are differently eliminated during hemodialysis. Residual renal function ensures a lower concentration of plasma phenols.