Dynamic changes of the composition of plasma HDL particles in patients with cardiac disease: Spotlight on sphingosine‐1‐phosphate/serum amyloid A ratio

Several epidemiological studies reported an inverse relationship between plasma high‐density lipoprotein (HDL) cholesterol levels and atherosclerotic cardiovascular disease (ASCVD). However, therapeutic interventions targeted at raising HDL‐cholesterol failed to improve cardiovascular outcomes, suggesting that HDL components distinct from cholesterol may account for the anti‐atherothrombotic effects attributed to this lipoprotein. Sphingosine‐1‐phosphate (S1P) and the acute phase protein serum amyloid A (SAA) have been identified as integral constituents of HDL particles. Evidence suggests that S1P and SAA levels within HDL particles may be affected by inflammation and oxidative stress, which are coexisting processes underlying ASCVD. Because SAA, an inflammation‐related marker, and S1P, an anti‐atherothrombotic marker, have relatively clear opposite characteristics among the HDL‐associated proteins, the approach of assessing the two markers simultaneously may provide new insights in clinical practice (S1P/SAA Index). This review focuses on evidence in support of the concept that the S1P/SAA Index may affect the HDL atheroprotective properties and may, therefore represent a potential target for therapeutic interventions.