Systematic Review of the Association between Lipoprotein-Associated Phospholipase A2 and Atherosclerosis

Evaluation of lipoprotein-associated phosholipase A2 and plaque burden/composition in young adults

OBJECTIVE

The total burden of subclinical coronary atherosclerosis is significant in young adults. Serum lipoprotein-associated phospholipase A2 (Lp-PLA2) is an established predictor of morbidity and mortality because of cardiovascular disease. The aim of the present investigation was to evaluate the relationship between subclinical coronary atherosclerosis and serum Lp-PLA2 concentrations in a population of young adults.

PATIENTS AND METHODS

A total of 261 individuals younger than 45 years of age who had undergone coronary computed tomography angiography were evaluated. The study group included 101 patients in whom coronary computed tomography angiography detected subclinical coronary atherosclerosis; the control group included 160 sex-matched and age-matched healthy control patients.

RESULTS

Serum Lp-PLA2 levels were increased significantly in the study group patients compared with the control patients (15.42±11.88 vs. 8.06±4.32 ng/ml, P<0.001). Furthermore, a positive correlation was identified between the Lp-PLA2 levels and the total number of plaques and diseased arteries (r=0.495, P<0.001, and r=0.621, P<0.001, respectively). The presence of mixed plaque composition was also correlated with the Lp-PLA2 levels (r=0.657, P<0.001). Multivariate regression analysis identified four independently significant predictors of subclinical coronary atherosclerosis: high-sensitivity C-reactive protein levels, tobacco use, uric acid levels, and serum Lp-PLA2 levels.

CONCLUSION

The presence of subclinical coronary atherosclerosis is associated independently with Lp-PLA2, and it has potential utility as a novel indicator of cardiovascular disease risk in the young adult population.

Modulation of oxidative stress, inflammation, and atherosclerosis by lipoprotein-associated phospholipase A2

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), also known as platelet-activating factor acetylhydrolase (PAF-AH), is a unique member of the phospholipase A(2) superfamily. This enzyme is characterized by its ability to specifically hydrolyze PAF as well as glycerophospholipids containing short, truncated, and/or oxidized fatty acyl groups at the sn-2 position of the glycerol backbone. In humans, Lp-PLA(2) circulates in active form as a complex with low- and high-density lipoproteins. Clinical studies have reported that plasma Lp-PLA(2) activity and mass are strongly associated with atherogenic lipids and vascular risk. These observations led to the hypothesis that Lp-PLA(2) activity and/or mass levels could be used as biomarkers of cardiovascular disease and that inhibition of the activity could offer an attractive therapeutic strategy. Darapladib, a compound that inhibits Lp-PLA(2) activity, is anti-atherogenic in mice and other animals, and it decreases atherosclerotic plaque expansion in humans. However, disagreement continues to exist regarding the validity of Lp-PLA(2) as an independent marker of atherosclerosis and a scientifically justified target for intervention. Circulating Lp-PLA(2) mass and activity are associated with vascular risk, but the strength of the association is reduced after adjustment for basal concentrations of the lipoprotein carriers with which the enzyme associates. Genetic studies in humans harboring an inactivating mutation at this locus indicate that loss of Lp-PLA(2) function is a risk factor for inflammatory and vascular conditions in Japanese cohorts. Consistently, overexpression of Lp-PLA(2) has anti-inflammatory and anti-atherogenic properties in animal models. This thematic review critically discusses results from laboratory and animal studies, analyzes genetic evidence, reviews clinical work demonstrating associations between Lp-PLA(2) and vascular disease, and summarizes results from animal and human clinical trials in which administration of darapladib was tested as a strategy for the management of atherosclerosis.