Serum FABP5 concentration is a potential biomarker for residual risk of atherosclerosis in relation to cholesterol efflux from macrophages

Cholesterol efflux capacity (CEC) from macrophages, the first step in the reverse cholesterol transport pathway, is inversely associated with residual risk for atherosclerotic cardiovascular disease. Fatty acid-binding protein 4 (FABP4) and FABP5 are expressed in both adipocytes and macrophages and play significant roles in the development of insulin resistance and atherosclerosis. Both FABP4 and FABP5 are secreted from cells, and their circulating levels are associated with insulin resistance and atherosclerosis. We investigated the association between CEC and levels of FABP4 and FABP5 in 250 subjects without any medications. CEC was positively correlated with HDL cholesterol level and negatively correlated with concentrations of high-sensitivity C-reactive protein (hsCRP) and FABP5, but not FABP4. Multiple regression analysis demonstrated that FABP5 concentration was an independent predictor of CEC after adjustment of age, gender and levels of HDL cholesterol and hsCRP. In 129 of the 250 subjects who underwent carotid ultrasonography, mean intima-media thickness was negatively correlated with CEC and was positively correlated with concentrations of FABP4 and FABP5. In conclusion, in contrast to FABP4, circulating FABP5 is associated with decreased CEC and carotid atherosclerosis, suggesting that FABP5 level is a regulatory factor of CEC and a potential biomarker for residual risk of atherosclerosis.