Serum paraoxonase/arylesterase activities in phenylketonuric patients on diet

Abstract

To compare serum paraoxonase/arylesterase (PON-aryl) activities in phenylketonuric (PKU) patients with high and low phenylalanine (Phe) blood concentration. Seventeen poorly controlled PKU children (off diet) underwent clinical and laboratory examinations before and after 30 days adhering to their special diet (on diet), whereas controls (N=24) were examined once. Lipid, lipoprotein levels and paraoxonase (PON 1) activities were measured with the Bayer Advia 1650 Clinical Chemistry System. Apolipoprotein AI (Apo AI) levels were determined by the Dade Behring BN ProSpec nephelometer, whereas total antioxidant capacity (TAC), PON-aryl and Phe levels were measured spectrophotometrically. Phe significantly differed among the groups. Lipids and lipoproteins, except high-density-lipoprotein-cholesterol (HDL-C) and Apo AI, were higher when off diet than those on diet. HDL-C and Apo AI were similar in patients and controls. TAC (0.99+/-0.19 mmol/l) was significantly lower when the patients were off diet than when they adhered to diet and controls (1.71+/-0.20 and 1.81+/-0.20 mmol/l P<0.001 respectively). PON 1 and PON-aryl activities (68+/-2 U/min/ml, 88+/-26 KU (min/ml) in children with high Phe were reduced as compared with those with low blood Phe levels (152+/-41 U/min/ml, 107+/-23 KU/min/ml P<0.001) and controls (146+/-43 U/min/ml, 109+/-41 KU/min/ml P<0.001). The enzyme activities positively correlated with HDL-C and Apo AI when PKU patients were on diet and controls as well as with TAC in all the groups, whereas negatively correlated with Phe levels. PON-aryl activities are strongly related to the dietary control of PKU patients.