title: Lipoprotein-associated phospholipase A2 activity is a marker of small, dense LDL particles in human plasma.
abstract: BACKGROUND
  Recent clinical studies showed that lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a predictor for incident atherosclerotic disease. We have previously shown that among the LDL subfractions, Lp-PLA(2) activity is preferentially associated with the atherogenic small, dense (sdLDL) particles in vitro. We investigated whether Lp-PLA(2) could be a marker of sdLDL in human plasma.
  
  
  METHODS
  One hundred and seventy-six individuals participated in the study. LDL subclass analysis was performed by polyacrylamide gel electrophoresis. Lp-PLA(2) activity and mass were determined in total plasma and in apolipoprotein B-depleted plasma (HDL-Lp-PLA(2)). Non-HDL-Lp-PLA(2) activity and mass were calculated by subtracting the HDL-Lp-PLA(2) from total plasma Lp-PLA(2).
  
  
  RESULTS
  On the basis of the LDL subclass analysis, participants were categorized into phenotype A and non-A (total cholesterol mass of the sdLDL subfractions < or =0.155 and >0.155 mmol/L, respectively). Unlike total plasma Lp-PLA(2) mass, total plasma Lp-PLA(2) activity and non-HDL-Lp-PLA(2) activity and mass were significantly higher in persons with phenotype non-A compared with persons with phenotype A, whereas HDL-Lp-PLA(2) activity and mass were lower in persons with phenotype non-A compared with phenotype A. Total plasma activity and non-HDL-Lp-PLA(2) activity and mass, but not Lp-PLA(2) mass, were correlated with sdLDL-cholesterol mass, proportion, and mean LDL particle size. In multiple regression analysis, total plasma and non-HDL-Lp-PLA(2) activities were the second best predictors of the presence of sdLDL particles in human plasma after serum triglyceride concentrations. At serum triglyceride concentrations >1.356 mmol/L, total plasma and non-HDL-Lp-PLA(2) activity added significantly to the prediction of the presence of sdLDL in plasma.
  
  
  CONCLUSIONS
  Lp-PLA(2) activity, but not the enzyme mass, is a marker of sdLDL in human plasma.
authors.affiliation: Department of Internal Medicine, Medical School, University of Ioannina, Greece.
authors.forename: Irene
authors.initials: I
authors.lastname: Gazi
authors.forename: Evangelia S
authors.initials: ES
authors.lastname: Lourida
authors.forename: Theodosios
authors.initials: T
authors.lastname: Filippatos
authors.forename: Vasilis
authors.initials: V
authors.lastname: Tsimihodimos
authors.forename: Moses
authors.initials: M
authors.lastname: Elisaf
authors.forename: Alexandros D
authors.initials: AD
authors.lastname: Tselepis
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D005260:Female; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D010741:Phospholipases A / Q000097:blood* / Q000378:metabolism*; D054467:Phospholipases A2
chemical_list: D015415:Biomarkers; D008077:Lipoproteins, LDL; D010741:Phospholipases A; D054467:Phospholipases A2; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase