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 treat ment as compared to healthy population. Methods. Patients (n=69) and control subjects (n=145) were from the area of Slavonski Bred, Croatia. Paraoxon was used as a substrate for measuring ba sal or sodium chloride-stimulated (NaCl-stimulated) paraoxonase activity, a nd 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 method s routinely used in medical-biochemical laboratories. Enzyme activities are expressed as international units per liter of serum or per mmol of HDL-cho lesterol (HDL-standardized activities). Results. Basal and NaCl-stimulated paraoxonase activity, as well as arylest erase activitiy 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-stimula ted paraoxonase activity standardized for HDL-cholesterol concentrations we re not significantly reduced in the hemodialyzed uremic patients as compare d to controls (86%, p=0.614 and 87%, p=0.720, respectively), contrary to ar ylesterase 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%, BE 18%, and 13%, respectively. Conclusion. Patients on long-term hemodialysis have decreased paraoxonase/a rylesterase activitiy, which might indicate a greater risk of premature ath erogenesis.