Paraoxonase-1 activities in children and adolescents with type 1 diabetes mellitus

Background: Paraoxonase-1 is an HDL-associated esterase that acts as an anti-atherogenic agent by protecting LDL from oxidation. This study investigates paraoxonase-1 activities in children and adolescents with type 1 diabetes mellitus and possible associations with other biochemical markers. Patients and methods: The study enrolled 82 children and adolescents with type 1 diabetes mellitus and 41 controls with similar age and gender distribution. Serum paraoxonase-1 arylesterase and salt-stimulated paraoxonase activities were assessed by measuring the rates of phenyl acetate and paraoxon hydrolysis, respectively; paraoxonase-1 lactonase activity and oxidized LDL were assessed by a pH-sensitive colorimetric assay and ELISA, respectively. Glycated haemoglobin HbA(1c) and lipid profile were assayed with an immunoturbidimetric method and commercially available kits, respectively. Results: We found lower paraoxonase-1 activities in diabetics when compared to controls. The decrease was statistically significant only for the lactonase activity, the difference being higher when referring to the subgroup with poor glycaemic control. The lactonase activity/HDL ratio was also lower in diabetics vs. controls, but without statistical significance. Both lactonase and arylesterase activities were negatively correlated with HbA1c in diabetics, but only the latter was statistically significant (rho = -0.21, P = 0.055; rho = -0.24, P = 0.03, respectively). A correlation coefficient of rho = 0.196 (P = 0.078) was found between oxidized LDL and HbA(1c). Conclusion: All paraoxonase-1 activities were lower in diabetic children and adolescents, but only the decrease in the lactonase activity was statistically significant. Although lipid profile and glycaemic control were altered in diabetics, no differences were observed between groups regarding oxidized LDL level.