Elevated serum ApoE levels are associated with bacterial infections in pediatric patients.

BACKGROUND/PURPOSE(S): We aimed to determine the variations in serum apolipoprotein E (ApoE) levels in pediatric patients with a variety of infectious diseases, and to investigate the potential mechanism of elevated ApoE serum levels during infection. METHODS: A total of 279 pediatric patients with a variety of infections and 58 normal controls were enrolled in this study. Serum ApoE levels were detected using an immunoturbidimetric assay. A mouse sepsis model was established to evaluate the expression of ApoE and its receptors by real-time polymerase chain reaction (RT-PCR) and Western blotting. RESULTS: Serum ApoE was markedly increased in cases with bacterial infections including sepsis, bacterial meningitis, and bacterial pneumonia, compared to healthy controls. No significantly elevated serum ApoE levels were observed in aseptic meningitis patients or mycoplasma pneumonia patients. The mice sepsis models showed a similar pattern of increased serum ApoE levels in the early stage of infections. We found reduced expression of ApoE and its receptors in the liver tissues in these mice models. CONCLUSION: Serum ApoE may represent a novel indicator for diagnosis of bacterial infections, especially sepsis, in pediatric patients. The decreased expression of low-density lipoprotein receptor (LDLR), LDL receptor-related protein (LRP), and heparin sulfate proteoglycan (HSPG) syndecan-1 (SDC1) may contribute to reduced ApoE clearance and accumulation in the blood.