Effect of lipoprotein lipase and hepatic triglyceride lipase activity on the distribution of apolipoprotein E among the plasma lipoproteins.
The independent roles of human lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) in determining the distribution of apolipoprotein E (apo E) among the plasma lipoproteins has been studied in vitro. In one series of three studies, postheparin plasma (10%) was incubated for 2 h with autologous plasma and the changes in the lipoprotein association of apo E after lipase exposure were determined after lipoprotein fractionation on 4% agarose columns. Specificity for LPL or HTGL was achieved by inhibition with goat anti-human HTGL or with 1 M NaCl, respectively. In another study, LPL and HTGL were partially purified from human postheparin plasma. The independent effects of these enzymes on the lipoprotein association of apo E were then examined after incubation of plasma in the absence or presence of one or both lipases. Data from both types of in vitro study showed that LPL-mediated triglyceride hydrolysis in the absence of HTGL activity was accompanied by a loss of apo E from triglyceride-rich lipoproteins, a gain or no change in the apo E-containing lipoproteins the size of intermediate density lipoproteins (IDL) and inconsistent changes in the apo E mass associated with high density lipoproteins (HDL). HTGL activity, on the other hand, in the absence of LPL, resulted in a redistribution of apo E from lipoproteins the size of IDL and a gain by those of HDL size. These studies thus support previous in vivo studies which pointed toward a specific role for HTGL in the processing of apo E containing IDL.
Gibson
J C
JC
Department of Medicine, University of Miami School of Medicine, FL.
Brown
W V
WV
D001053:Apolipoproteins / Q000097:blood; D001057:Apolipoproteins E / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D008049:Lipase / Q000502:physiology*; D008071:Lipoprotein Lipase / Q000502:physiology*; D008074:Lipoproteins / Q000097:blood*; D053419:Lipoproteins, IDL; D008099:Liver / Q000201:enzymology*
D001053:Apolipoproteins; D001057:Apolipoproteins E; D008074:Lipoproteins; D053419:Lipoproteins, IDL; D008049:Lipase; D008071:Lipoprotein Lipase