title: Serum paraoxonase activity in uremic predialysis and hemodialysis patients.
abstract: BACKGROUND
  Paraoxonase (PON1) is a high-density lipoprotein (HDL)-associated enzyme and has been shown to reduce the susceptibility of low-density lipoprotein (LDL) to lipid peroxidation. This study aimed to investigate the activity and phenotype distribution of serum paraoxonase in uremic patients, and to evaluate the correlations of uremia-associated substances (urea, creatinine (Cr) and uric acid) with paraoxonase activity.
  
  
  METHODS
  Twenty-eight patients with chronic renal failure (CRF), 44 patients with CRF undergoing hemodialysis (HD) and 26 healthy controls were included in this study. Paraoxon or phenylacetate was used as a substrate for measuring paraoxonase and arylesterase activity, respectively. The double substrate method was used to assign phenotypes. Serum lipid parameters were determined by routine laboratory methods.
  
  
  RESULTS
  Paraoxonase activity, HDL-cholesterol and apolipoprotein (apo) AI levels were found to be significantly lower in HD patients than in controls. However, HDL-standardized paraoxonase activity (PON activity/HDL) was not different in the HD patients compared to controls. Arylesterase activity was significantly lower in both CRF and HD patients than in controls. Paraoxonase phenotype distribution was not different among the groups according to the double substrate method. Serum paraoxonase and arylesterase activities correlated inversely with serum urea and Cr levels.
  
  
  CONCLUSIONS
  Patients on long-term HD have reduced paraoxonase/arylesterase activities and this could be related to reduced HDL-cholesterol and apo AI levels, as well as increased urea and Cr levels in uremia.
authors.affiliation: Department of Biochemistry, Uludag University Medical Faculty, Bursa, Turkey. mdirican@uludag.edu.tr
authors.forename: Melahat
authors.initials: M
authors.lastname: Dirican
authors.forename: Ramazan
authors.initials: R
authors.lastname: Akca
authors.forename: Emre
authors.initials: E
authors.lastname: Sarandol
authors.forename: Kamil
authors.initials: K
authors.lastname: Dilek
mesh_terms: D000328:Adult; D016632:Apolipoprotein A-I / Q000097:blood; D043303:Aryldialkylphosphatase / Q000097:blood*; D002265:Carboxylic Ester Hydrolases / Q000097:blood; D016022:Case-Control Studies; D008076:Cholesterol, HDL / Q000097:blood; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis; D014508:Urea / Q000097:blood; D014511:Uremia / Q000097:blood*
chemical_list: D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D014508:Urea; D003404:Creatinine; D002265:Carboxylic Ester Hydrolases; C019734:arylesterase; D043303:Aryldialkylphosphatase