EL and LPL cooperate to promote TRL lipolysis in vivo.

A. Volcano plot of 77 plasma triglyceride (TG) species from plasma of WT vs Lipg^-/- mice after overnight fasting (filled black circles) and 7 hours (white circles) after oral fat tolerance test. Lipids were measured by liquid-chromatography tandem mass spectrometry (LC-MS) as described in the Materials and Methods. Plot shows fold change in Lipg^-/- mice vs WT (x-axis; logarithmic base-2 scale) with the p-value (y-axis; logarithmic base-10 scale). Vertical dotted lines indicate two-fold change, and horizontal dotted line corresponds to P<0.05. B. (left and right) Plasma concentration of TG species in the red line from (A) as measured by LC-MS at the indicated timepoints. C. Volcano plot of 28 plasma phosphatidylcholine (PC) species from plasma of WT vs Lipg^-/- mice after overnight fasting (filled black circles) and 7 hours (white circles) after oral fat tolerance test. Lipids were measured by liquid-chromatography tandem mass spectrometry (LC-MS) as described in the Materials and Methods. D. (left and right) Plasma concentration of PC species in the red line from (C) as measured by LC-MS at the indicated timepoints. E. In vitro TG lipase activity of EL and LPL conditioned media on ³H-triolein labeled TRL-like emulsions. Emulsions were incubated with the indicated volumes of EL or LPL-containing conditioned medium from COS7 cells infected with EL- or LPL-expressing adenovirus. Release of ³H-oleate was used to measure TG lipase activity. F. In vitro phospholipase activity on ³H-triolein labeled TRL-like emulsions in reactions with LPL of the indicated volume and increasing volumes of EL WT or EL S169A conditioned media. G. In vitro phospholipase activity of EL and LPL conditioned media on ¹⁴C-DPPC-labeled TRL-like emulsions, as shown in (A-B). H. TG-lipase activity on ¹⁴C-DPPC labeled TRL-like emulsions in reactions with LPL of the indicated volume and increasing volumes of EL WT or EL S169A conditioned media. I. TG-lipase activity on ³H-triolein labeled human VLDLs incubated with recombinant EL WT, LPL or a combination of EL WT and LPL. Red dotted line indicates the sum of the mean activities for the EL WT (red bar) and LPL (blue bar) groups. B and C: *P<0.05, *student’s unpaired T-test comparing the indicated groups. E-H: ****P<0.0001, two-way ANOVA for interaction term of indicated groups and sample volume term (X-axis). I: ****P<0.0001, one-way ANOVA comparing EL WT + LPL group (white bar) with other groups. Data is expressed as mean ± S.E.M.