Endogenous ANGPTL4 protein was immunoprecipitated as described above from 2 mL of sample consisting of equal volumes of pooled normal human serum and PBS using polyclonal anti-ANGPTL4 antibody covalently coupled to tosyl-activated magnetic beads (ThermoFisher Scientific). To prepare ANGPTL4/8 plasmin-generated products in assay buffer, recombinant ANGPTL4/8 (200 nM) was incubated with tPA (0.2 nM) and plasminogen (200 nM) together in Abnova assay buffer at 37 °C for 10 min. The reaction was quenched by adding aprotinin (50 µM). To prepare ANGPTL4/8 plasmin-generated products in culture media from LPL-stable expressing cells, the cells were first incubated with 100 nM of recombinant ANGPTL4/8 for 1 h at 37 °C prior to the addition of 10 nM tPA and 30 nM plasminogen. The cells were incubated at 37 °C for another 30 min. Cell culture media was removed, and the reaction was quenched by adding aprotinin (50 µM). One sample aliquot was used for Western blotting with anti-ANGPTL4 antibodies. Another aliquot was enriched using polyclonal anti-ANGPTL4 antibody covalently coupled to tosyl-activated magnetic beads. Magnetic beads were extensively washed with PBS and captured ANGPTL4 cleavage products were eluted using 1% acetic acid followed by drying the samples under nitrogen to remove acetic acid. Digests of endogenous ANGPTL4 and plasmin-generated ANGPTL4 fragments were characterized as described in SI Appendix, Materials and Methods.