Quantification of human plasma phospholipid transfer protein (PLTP): relationship between PLTP mass and phospholipid transfer activity

A sensitive sandwich-type enzyme-linked immunosorbent assay (ELISA) for hum an plasma phospholipid transfer protein (PLTP) has been developed using a m onoclonal capture antibody and a polyclonal detection antibody. The ELISA a llows for the accurate quantification of PLTP in the range of 25-250 ng PLT P/assay. Using the ELISA, the mean plasma PLTP concentration in a Finnish p opulation sample (n = 159) was determined to be 15.6 +/- 5.1 mg/l, the valu es ranging from 2.30 to 33.4 mg/l. PLTP mass correlated positively with HDL -cholesterol (r = 0.36, P < 0.001), apoA-I (r = 0.37, P < 0.001), apoA-II ( r = 0.20, P < 0.05), Lp(A-I) (r = 0.26, P = 0.001) and Lp(A-I/A-II) particl es (r = 0.34, P < 0.001), and negatively with body mass index (BMI) (r = - 0.28, P < 0.001) and serum triacylglycerol (TG) concentration (r = - 0.34, P < 0.001). PLTP mass did not correlate with phospholipid transfer activity as measured with a radiometric assay. The specific activity of PLTP, i.e. phospholipid transfer activity divided by PLTP mass, correlated positively with plasma TG concentration (r = 0.568, P < 0.001), BMI (r = 0.45, P < 0.0 01), apoB (r = 0.45, P < 0.001), total cholesterol (r = 0.42, P < 0.001), L DL-cholesterol (r = 0.34, P < 0.001) and age (r = 0.36, P < 0.001), and neg atively with HDL-cholesterol (r = - 0.33, P < 0.001), Lp(A-I) (r = - 0.21, P < 0.01) as well as Lp(A-I/A-II) particles (r = - 0.32, P < 0.001). When b oth PLTP mass and phospholipid transfer activity were adjusted for plasma T G concentration, a significant positive correlation was revealed (partial c orrelation, r = 0.31, P < 0.001). The results suggest that PLTP mass and ph ospholipid transfer activity are strongly modulated by plasma lipoprotein c omposition: PLTP mass correlates positively with parameters reflecting plas ma high density lipoprotein (HDL) levels, but the protein appears to be mos t active in subjects displaying high TG concentration. (C) 2000 Elsevier Sc ience Inland Ltd. All rights reserved.