Abstract 119: Identifying and Quantifying Eight ApoA-I HDL Subspecies by a Novel Modified Sandwich ELISA
HDL-cholesterol is a well-established independent risk factor used in CVD risk stratification. However, the cardioprotective effect of HDL-cholesterol is challenged by genetic studies and pharmaceutical trials, which do not support the causal relationship between increased HDL-cholesterol levels and CVD. Previously, our lab found that HDL can be classified into subspecies based on the presence of apoC-III, where for example 7% of the total plasma apoA-I in HDL has apoC-III. We also showed that the apoA-I concentration of HDL that has apoC-III predicts increased risk of CHD, whereas that of HDL that does not have apoC-III predicts decreased risk of CHD. We hypothesized that some of the many other proteins that are located in HDL are present in apoA-I HDL subspecies.
We developed a novel sandwich ELISA to measure apoA-I in HDL that is associated with a specific protein of interest, and applied it to apoA-II, apoC-III, and apoE, which define known subspecies of apoA-I HDL. We also applied the ELISA to apoC-I, apoC-II, and plasminogen, to determine whether their association with HDL constitutes a subspecies of apoA-I HDL, and in what concentrations they exist in HDL. We confirmed the existence of all the apoA-I lipoprotein subtypes using pooled plasma samples collected from healthy men and women (age: 40±14 (mean±SD), triglyceride: 116±63 mg/dl, LDL-cholesterol: 118±28 mg/dl, HDL-cholesterol: 45±10 mg/dl). The concentration (percentage) of total plasma apoA-I in HDL associated with apoA-II was 103±11 mg/dl (71±12%), with apoC-I was 23±4 mg/dl (16±2%), with apoC-II was 4±1 mg/dl (2±1%), with apoC-III was 9±3 mg/dl (6±1%), with apoE was 8±5 mg/dl (5±3 %) and with plasminogen was 4±1 mg/dl (3±1%). The results for apoA-II, apoC-III, and apoE are consistent with previously reported values. In conclusion, we established a convenient sandwich ELISA, which demonstrated the existence of new apoA-I HDL subspecies that are defined by presence of apoC-I, apoC-II, and plasminogen, as well as known subspecies of apoA-I HDL; and we quantified the concentration of such subspecies. Future studies will investigate these abundant HDL subtypes in relation to CVD risk.
Author Disclosures: R. Yamamoto: None. J.D. Furtado: None. F.M. Sacks: None.
- © 2015 by American Heart Association, Inc.