Elevated circulating levels of lipoprotein-associated phospholipase A2 in obese children

Obesity and cardiovascular disease (CVD) often co-exist, but the pathophysiologic mechanisms that link the two are not fully understood. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is involved in the modification of lipids within atheromatous plaques. Recently, circulating Lp-PLA2 was found to be predictive of thromboembolic episodes in adults, independently of a variety of other potential risk factors, including markers of inflammation, renal function, and hemodynamic stress. However, the function of this lipase and its importance as a biomarker in childhood obesity is much less studied. The aim of the study was to study Lp-PLA2, a non-traditional risk factor of CVD, in obese children.

Sixty-seven lean [39 boys and 28 girls, mean body mass index (BMI) z-score -0.2±0.8] and 66 obese (32 boys and 34 girls, mean BMI z-score 4.4±1.2) age-matched (p=0.251) children, aged 6-12 years, were studied. BMI z-score was calculated based on the Greek BMI growth curves, and children were categorized as obese according to the Cole criteria. All children underwent physical examination and a fasting morning blood sample was obtained for glucose, insulin, lipid profile, and Lp-PLA2 assessment. Plasma concentrations of Lp-PLA2 were determined by a commercially available Lp-PLA2 enzyme-linked immunosorbent assay kit (PLAC Test), while other measurements were performed using standard methods.

Plasma Lp-PLA2 levels were significantly higher in obese children (322.5±77.8 ng/mL) compared with normal-weight ones (278.0±64.4 ng/mL, p<0.001). Lp-PLA2 concentrations were significantly correlated with the BMI z-score (p=0.004). Receiver operating characteristic analysis on Lp-PLA2 values resulted in significant areas under the curve (AUC) for distinguishing between obese and normal-weight groups of children (AUC, 0.726; p<0.001).

We found significantly higher Lp-PLA2 levels in obese children than lean controls. Interestingly, they all had levels >200 ng/mL, which are considered to correlate with atherosclerosis and a high thromboembolic risk in adults. The positive correlation of Lp-PLA2 with BMI suggests that Lp-PLA2 might be the link between obesity and increased cardiovascular risk, which can be elevated even at a very young age. Measurement of Lp-PLA2 in plasma could therefore represent a further biomarker for assessing increased CVD risk in obese children and adolescents.