Serum paraoxonase activities in hemodialyzed uremic patients: cohort study.

AIM: To determine whether paraoxonase activity, paraoxonase phenotypes, and lipid status are altered in uremic patients on long-term hemodialysis treatment as compared to healthy population. METHODS: Patients (n = 69) and control subjects (n = 145) were from the area of Slavonski Brod, Croatia. Paraoxon was used as a substrate for measuring basal or sodium chloride-stimulated (NaCl-stimulated) paraoxonase activity, and phenylacetate for measuring arylesterase activity. The double substrate method was used to assign phenotypes. Cholesterol, triglycerides, and high-density lipoprotein cholesterol (HDL-cholesterol) were determined by methods routinely used in medical-biochemical laboratories. Enzyme activities are expressed as international units per liter of serum or per mmol of HDL-cholesterol (HDL-standardized activities). RESULTS: Basal and NaCl-stimulated paraoxonase activity, as well as arylesterase activity expressed per serum volume, were significantly lower in the hemodialyzed uremic patients compared to the controls; 69% (p < 0.001), 73% (p < 0.001) and 49%, (p < 0.001), respectively. However, basal and NaCl-stimulated paraoxonase activity standardized for HDL-cholesterol concentrations were not significantly reduced in the hemodialyzed uremic patients as compared to controls (86%, p = 0.614 and 87%, p = 0.720, respectively), contrary to arylesterase activity, which remained significantly lower (72%, p < 0.001). The distribution of paraoxonase phenotypes in hemodialyzed uremic patients and controls was as follows: AA 45% and 39%, AB 37% and 48%, BB 18%, and 13%, respectively. CONCLUSION: Patients on long-term hemodialysis have decreased paraoxonase/arylesterase activity, which might indicate a greater risk of premature atherogenesis.