Abstract 325: HDL Binding Rates for MPO: An Index of Functionality?

Abstract

Listen

Translate article

Statement of Problem: Measurements of high density lipoprotein (HDL) function are reported to be more predictive for atheroprotection than measurements of HDL cholesterol. Unfortunately, bioassays of HDL function are complex, manual and time-consuming, making them impractical for routine clinical use. As such, well-standardized and easy-to-use assays of HDL function are desperately needed to make better informed clinical decisions. We are developing a panel of biolayer interferometry ( BLI ) assays on the Octet Red (forteBio, Inc) that measure HDL binding rates for biomolecules that regulate HDL function. Previously we showed that hypochlorous acid-modified HDL (ox-HDL) bound paraoxonase 1, myeloperoxidase (MPO) and cholesteryl ester transfer protein at faster rates than native HDL (n-HDL). Based on these data, we hypothesize that BLI assays of HDL binding rates might be useful for assessing functionality in vivo. Methods: To test this hypothesis, the biophysics of HDL interactions with MPO was examined in rodent models of metabolic syndrome and hypercholesterolemia and in patients with documented cardiovascular disease (CVD). Briefly, HDL was immunocaptured onto anti-apoA-I biosensors, incubated in a standardized solution of MPO and binding rates determined in ∼3.5 min/sample. Results: HDL from fructose-fed hamsters tended to bind MPO at faster rates than from chow-fed hamsters (300% of control p<0.07, n=6). HDL from hypercholesterolemic Ldlr -/- mice bound MPO at much faster rates than HDL from control mice (175% of control p<0.05, n=4). HDL from patients with CVD bound MPO at faster rates than HDL from control humans (280% of control p<0.004, n=6). Conclusions: HDL in hamsters with metabolic syndrome, mice with hypercholesterolemia and patients with CVD appears to bind MPO at faster rates than their corresponding controls. Automated BLI assays make it possible to complete large scale clinical studies in a reasonable time frame. Finally biophysical interactions of HDL with biomolecules such as MPO may be a useful approach for quantifying HDL functionality.