Osteoprotegerin, IL-6, IL-1, TNF-α and TGF-β concentrations during acetate-free biofiltration

To ascertain the effect of acetate-free biofiltration (AFB), performed with polyacrilonitrile filters, on serum concentrations of osteoprotegerin (OPG) and other bone-acting cytokines (interleukin (IL) IL-1, IL-6, tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta)) in end-stage renal disease (ESRD) patients, we evaluated these parameters during an AFB session and 24 hr after it ended. In second time we verified the existence of eventual correlations among serum levels of all these cytokines at different times. We investigated 48 subjects: 24 healthy volunteers (controls) (12 females, 12 males, mean age 55 +/- 9 yrs) and 24 ESRD patients (12 females, 12 males, mean age 58 +/- 6.7 yrs, mean dialytic age 2.7 +/- 1.6 yrs, residual glomerular filtration rate (GFR) 2.3 +/- 0.6 ml/min). All dialyzed patients received regular AFB with polyacrilonitrile filters for 4 hr thrice-weekly. Statistical analysis showed significant increase in basal serum OPG, IL-6 and TNF-alpha concentrations in dialyzed patients compared to controls, while it did not show significant variations for the other cytokines. During the dialytic session, OPG and TGF-beta concentrations did not show significant variations, while serum TNF-alpha, IL-6 and IL-1 levels significantly decreased from the 1st hour of AFB. None of the cytokines showed significant differences between basal and interdialytic values. We did not find correlations between OPG, IL-1, IL-6, TNF-alpha and TGF-beta concentrations during hemodialytic sessions and during the interdialytic interval. It is our opinion that the lack of correlation between serum concentrations, observed in our study, could not exclude the presence of local interferences between OPG and the other cytokines.