Serum paraoxonase activity changes in uremic and kidney-transplanted patients

Serum paraoxonase (PON) is a high-density lipoprotein (HDL)-associated hydr olase, which inhibits low-density lipoprotein oxidation. Uremic and kidney- transplanted patients have an increased risk of atherosclerosis, to which a n increased lipoprotein oxidation may contribute. The aim of our study was to determine whether the PON activity or phenotype is altered in uremic and kidney-transplanted patients, and to compare the values with those, of hea lthy controls. 117 uremic patients on long-term hemodialysis treatment, 115 renal-transplanted patients, and 110 healthy controls were involved in the study. The PON activity was significantly reduced in the uremic patients c ompared to controls (PON 101.36 +/- 30.12 vs, control 188.05 +/- 58.96 U/ml ; p < 0.001), while in kidney-transplanted patients the values were almost identical to those of controls (PON 161.5 +/- 35.39 U/ml). The different im munosuppressive drug combinations did not influence PON activity. To assess whether the altered PON activity was due to a decrease HDL level, we stand ardized the enzyme activity for the HDL concentration (PON/HDL ratio). We f ound that the standardized enzyme activity was lower in the uremic (102.7 /- 54.8) and kidney-transplanted patients (144.5 +/- 32.7) when compared to controls (194.5 +/- 94.5; p < 0.001). The phenotypic distribution of PON i n uremic, renal transplant and control patients are as follows: AA 66.67, 5 6.48 and 66.67%; AB 31.62, 33.3 and 26.67%; BE 1.71, 10.19 and 6.67%. We co nclude that the decreased PON/HDL and PON/apoA-1 ratios may lead to a reduc tion in the antioxidant capacity of HDL, which might contribute to the acce lerated development of atherosclerosis in uremic and kidney-transplanted pa tients.