OBJECTIVES: The goal of this study was to examine the association between paraoxonase-1 (PON1) activity and concentration and the severity and extent of coronary artery disease (CAD). BACKGROUND: Paraoxonase-1, a high-density lipoprotein-associated enzyme, is proposed to have an antiatherogenic effect by protecting low-density lipoproteins against oxidation. METHODS: We studied PON1 activity and concentration in 107 patients with known or suspected CAD referred for cardiac catheterization. Based on visual estimation of coronary angiograms, subjects were classified as having no or mild CAD (<50% stenosis) and significant CAD (> or =50% stenosis). Quantitative coronary angiography (QCA) was used to estimate the indexes of severity, extent, and overall atheroma burden of CAD. RESULTS: We found lower values of PON1 activity and concentration (p = 0.003 and p = 0.016, respectively) in the group with significant CAD as compared with the group with no or mild CAD. The PON1 activity was significantly inversely correlated with CAD severity (r = -0.364, p < 0.001), extent (r = -0.221, p = 0.022), and atheroma burden (r = -0.277, p = 0.004). Similarly, PON1 concentration correlated with CAD severity (r = -0.306, p = 0.001) and atheroma burden (r = -0.229, p = 0.017). In multiple regression analysis, gender and PON1 activity were significant determinants of the severity of CAD independently of age, hypertension, smoking, abnormal glucose regulation, and high-density lipoprotein cholesterol. CONCLUSIONS: Our results indicate that PON1 activity and concentration are lower in subjects with significant CAD, and that there is a significant relationship between PON1 activity and concentration and CAD assessed by QCA.
We have characterized the molecular basis for familial hepatic lipase (HL) deficiency in a Finnish family. In the propositus, the HL deficiency results from compound heterozygosity for two rare HL gene mutations, a previously unknown missense mutation designated L334F and the previously reported T383M mutation. These mutations were introduced into human HL cDNA by site-directed mutagenesis and the constructs expressed in COS-1 cells. In the homogenate of COS-1 cell transfected with the L334F mutant cDNA, a high amount of inactive protein accumulated. In the media of L334F transfected cells, 30% of the wild type activity and 80% of wild type mass were detected. The lysates of COS-1 cells transfected with the T383M mutant cDNA contained 39% of wild type HL activity and 34% of wild type HL mass. In the media of COS-1 cells transfected with the T383M cDNA construct, 50% of wild type HL mass but only 6% of wild type activity was present. The single amino acid substitutions present in L334F and T383M are therefore sufficient to severely affect the HL enzyme. These defects explain the HL-deficient phenotype of the individual carrying the two mutations. The lipoprotein phenotype associated with compound heterozygosity for L334F and T383M mutations is characterized by a slight increase in the buoyant low density lipoprotein (LDL) fraction and an increase in the light high density lipoprotein (HDL) fractions, HDL2a and HDL2b. These results demonstrate that lipoprotein changes occurring in HL deficiency are difficult to identify and support the hypothesis that HL is important in HDL remodeling and metabolism in vivo.
