Decreased paraoxonase 1 (PON1) lactonase activity in hemodialyzed and renal transplanted patients. A novel cardiovascular biomarker in end-stage renal disease

Human paraoxonase-1 (PON1) has also been described as a lactonase. Decreased PON1 lactonase activity was found to be a predictor of cardiovascular disease. Homocysteine thiolactonase activity may prevent proteins from homocysteinylation and is thought to be a protective factor against the progression of atherosclerosis. Previous studies have demonstrated decreased PON1 paraoxonase activity in hemodialyzed (HD) and renal transplant (TRX) patients; however, lactonase activity has not been investigated. We aimed to determine the paraoxonase and lactonase activities and to clarify the relationship between lactonase activity and a set of cardiovascular risk factors, such as homocysteine, cystatin C and asymmetric dimethylarginine (ADMA) levels, in HD and TRX patients and in healthy controls. One hundred and eight HD and 78 TRX patients and 63 healthy controls were involved in the study. Paraoxonase and lactonase activities (paraoxon and gamma-thiobutyrolactone as substrates) were measured spectrophotometrically. ADMA level was determined with sandwich enzyme-linked immunosorbent assay. Both HD and TRX patients had significantly lower lactonase activities compared to the control group (P