This article is available online at http://www.jlr.org High density lipoprotein (HDL) levels have long believed to be cardioprotective ( 1 ) through a variety of processes, including reverse cholesterol transport in which excess cholesterol is taken to the liver for excretion ( 2 ). However, recent studies have highlighted the need to better understand the cardioprotective role of HDL. For example, two recent Mendelian randomization studies found that single nucleotide polymorphisms (SNP) that predict plasma HDL cholesterol (HDL-C) variance were not associated with myocardial infarction (MI) ( 3, 4 ). Moreover, a recent drug trial with torcetrapib, a cholesterol ester transport protein inhibitor, found that although torcetrapib increased levels of HDL and lowered deleterious low density lipoprotein (LDL) levels, it did not affect atherosclerotic measures and paradoxically led to an increase in adverse cardiovascular events ( 5 ). In addition, a recent large randomized clinical trial did not show a benefi t of niacin in preventing adverse cardiovascular outcomes, despite improved levels of HDL-C and triglycerides in the treatment group ( 6 ). These results refocus attention on the many aspects of HDL biology that are not captured by serum measurements of HDL, such as its paraoxonase 1 (PON1) activity, which itself is inversely associated with cardiovascular and other human diseases.The activity of PON1 , a liver-produced glycoprotein enzyme bound to the surface of HDL, is consistently correlated with atherosclerotic vascular disease and end-organ damage ( 7-9 ). PON1 is at least partially responsible for the cardioprotective inhibitory effects of HDL on LDL peroxidation ( 10-12 ), and it also has been demonstrated to hydrolyze oxidized lipid or lipid hydroperoxides in LDL ( 13 ). Inactivation of PON1 reduced the ability of HDL to Abstract HDL-associated paraoxonase 1 (PON1) activity has been consistently associated with cardiovascular and other diseases. Vitamins C and E intake have previously been positively associated with PON1 in a subset of the Carotid Lesion Epidemiology and Risk (CLEAR) cohort. The goal of this study was to replicate these fi ndings and determine whether other nutrient intake affected PON1 activity. To predict nutrient and mineral intake values, 1,402 subjects completed a standardized food frequency survey of their dietary habits over the past year. Stepwise regression was used to evaluate dietary and covariate effects on PON1 arylesterase activity. Five dietary components, cholesterol ( P < 2.0 × 10 ؊ 16 ), alcohol ( P = 8.51 × 10 ؊ 8 ), vitamin C ( P = 7.97 × 10 ؊ 5 ), iron ( P = 0.0026), and folic acid (0.037) were independently predictive of PON1 activity. Dietary cholesterol was positively associated and predicted 5.5% of PON1 activity, second in variance explained. This study presents a novel fi nding of dietary cholesterol, iron, and folic acid predicting PON1 activity in humans and confi rms prior reported associations, including that with vitamin C. Identifying and understanding en...

BackgroundRecent data suggest that high‐density lipoprotein cholesterol (HDL‐C) levels are likely not in the causative pathway of atheroprotection, shifting focus from HDL‐C to its subfractions and associated proteins. This study's goal was to determine which HDL phenotype was the better predictor of carotid artery disease (CAAD).Methods and ResultsHDL‐2 and HDL‐3 were measured in 1725 participants of European ancestry in a prevalent case‐control cohort study of CAAD. Stratified analyses were conducted for men (n=1201) and women (n=524). Stepwise linear regression was used to determine whether HDL‐C, HDL‐2, HDL‐3, or apolipoprotein A1 was the best predictor of CAAD, while adjusting for the confounders of censored age, diabetes, and current smoking status. In both men and women, HDL‐3 was negatively associated with CAAD (P=0.0011 and 0.033 for men and women, respectively); once HDL‐3 was included in the model, no other HDL phenotype was significantly associated with CAAD. Addition of paraoxonase 1 activity to the aforementioned regression model showed a significant and independent (of HDL‐3) association with CAAD in men (P=0.001) but not in the smaller female subgroup.ConclusionsThis study is the first to contrast the associations of HDL‐2 and HDL‐3 with CAAD. We found that HDL‐3 levels were more predictive of CAAD status than HDL‐2, HDL‐C, or apolipoprotein A1. In addition, for men, paraoxonase 1 activity improved the overall model prediction for CAAD independently and additively with HDL‐3 levels. Further investigation into the molecular mechanisms through which HDL‐3 is associated with protection from CAAD is warranted.

Background. Paraoxonase 1 (PON1) enzymatic activity has been consistently predictive of cardiovascular disease, while the genotypes at the four functional polymorphisms at PON1 have not. The goal of this study was to identify additional variation at the PON gene cluster that improved prediction of PON1 activity and determine if these variants predict carotid artery disease (CAAD). Methods. We considered 1,328 males in a CAAD cohort. 51 tagging single-nucleotide polymorphisms (tag SNPs) across the PON cluster were evaluated to determine their effects on PON1 activity and CAAD status. Results. Six SNPs (four in PON1 and one each in PON2/3) predicted PON1 arylesterase (AREase) activity, in addition to the four previously known functional SNPs. In total, the 10 SNPs explained 30.1% of AREase activity, 5% of which was attributable to the six identified predictive SNPs. We replicate rs854567 prediction of 2.3% of AREase variance, the effects of rs3917510, and a PON3 haplotype that includes rs2375005. While AREase activity strongly predicted CAAD, none of the 10 SNPs predicting AREase predicted CAAD. Conclusions. This study identifies new genetic variants that predict additional PON1 AREase activity. Identification of SNPs associated with PON1 activity is required when evaluating the many phenotypes associated with genetic variation near PON1.

In contrast with mammalian cells, little is known about the control of Ca2+ entry into primitive protozoans. Here we report that Ca2+ influx in pathogenic Trypanosoma brucei can be regulated by phospholipase A2 (PLA2) and the subsequent release of arachidonic acid (AA). Several PLA2 inhibitors blocked Ca2+ entry; 3-(4-octadecyl)-benzoylacrylic acid (OBAA; IC50 0.4+/-0.1 microM) was the most potent. We identified in live trypanosomes PLA2 activity that was sensitive to OBAA and could be stimulated by Ca2+, suggesting the presence of positive feedback control. The cell-associated PLA2 activity was able to release [14C]AA from labelled phospholipid substrates. Exogenous AA (5-50 microM) also initiated Ca2+ entry in a manner that was inhibited by the Ca2+ antagonist La3+ (100 microM). Ca2+ entry did not depend on AA metabolism or protein kinase activation. The cell response was specific for AA, and fatty acids with greater saturation than tetraeicosanoic acid (AA) or with chain lengths less than C20 exhibited greatly diminished ability to initiate Ca2+ influx. Myristate and palmitate inhibited PLA2 activity and also inhibited Ca2+ influx. Overall, these results demonstrate that Ca2+ entry into T. brucei can result from phospholipid hydrolysis and the release of eicosanoic acids.

Cholesterol carried on HDL (HDL-C) has long been believed to be cardioprotective, based on consistent epidemiologic fi ndings of an inverse relationship between incident CVD and HDL-C levels in subjects healthy at baseline ( 1, 2 ). Estimates from the Framingham Heart Study found that risk of myocardial infarction (MI) increased by 25% for each 5 mg/dl decrease in HDL-C below median values of HDL-C for both healthy men and women ( 2 ). Similar fi ndings of the cardioprotective effects of HDL-C have also been reported in subjects with CVD at baseline ( 3 ).In confl ict with these epidemiologic fi ndings, recent attempts to establish a causal relationship between HDL-C Abstract Recent studies have failed to demonstrate a causal cardioprotective effect of HDL cholesterol levels, shifting focus to the functional aspects of HDL. Phospholipid transfer protein (PLTP) is an HDL-associated protein involved in reverse cholesterol transport. This study sought to determine the genetic and nongenetic predictors of plasma PLTP activity (PLTPa), and separately, to determine whether PLTPa predicted carotid artery disease (CAAD). PLTPa was measured in 1,115 European ancestry participants from a casecontrol study of CAAD. A multivariate logistic regression model was used to elucidate the relationship between PLTPa and CAAD. Separately, a stepwise linear regression determined the nongenetic clinical and laboratory characteristics that best predicted PLTPa. A fi nal stepwise regression considering both nongenetic and genetic variables identifi ed the combination of covariates that explained maximal PLTPa variance. PLTPa was signifi cantly associated with CAAD (7.90 × 10 ؊ 9 ), with a 9% decrease in odds of CAAD per 1 unit increase in PLTPa (odds ratio = 0.91). Triglyceride levels ( P = 0.0042), diabetes ( P = 7.28 × 10 ؊ 5 ), paraoxonase 1 (PON1) activity ( P = 0.019), statin use ( P = 0.026), PLTP SNP rs4810479 ( P = 6.38 × 10 ؊ 7 ), and PCIF1 SNP rs181914932 ( P = 0.041) were all signifi cantly associated with PLTPa. PLTPa is signifi cantly inversely correlated with CAAD. Furthermore, we report a novel association between PLTPa and PON1 activity, a known predictor of