Usefulness of plasma and apolipoprotein B-depleted serum samples in paraoxonase 1 assessment

Abstract

Background: Paraoxonase 1 (PON1) is closely associated with the antioxidant, anti-inflammatory, and antiatherosclerotic functions of HDL. Although many clinical studies have evaluated the relationship between PON1 activity and various diseases, there are inconsistencies in sample preparation methods and substrate selection for PON1 analysis. Moreover, depending on the selected substrates, various types of PON1 activities can be measured, which would be an obstacle of dissemination of clinical practice. Here, we investigated differences between three PON1 activity types according to sample preparation procedures. Methods: Samples were prepared from serum, plasma with or without calcium addition, HDL isolated by ultracentrifugation, and apolipoprotein B-depleted serum (BDS). Using these various sample types, PON1 protein concentration and activities using three substrate types (p-nitrophenyl acetate, paraoxon, and γ-thiobutyrolactone) were evaluated. PON1 distributions in HDL subfractions from serum and BDS samples were also investigated. Results: PON1 activities in plasma were maintained by immediate calcium addition similar to those in serum, suggesting that plasma could be used for assessing PON1 instead of serum in which PON1 can be transported to apolipoprotein B-containing lipoproteins. In contrast, HDL isolated from plasma had significantly lower PON1 protein concentrations. PON1 activities, protein concentration, and distributions in BDS sample showed similar to those in serum samples than those in HDL sample. Conclusions: This study revealed the advantages of using plasma with calcium addition and BDS as specimens that better reflect the in vivoenvironment for PON1 assessment. Focusing on each of three PON1 activity types might further enhance the clinical significance of PON1 testing.