Expression of human lecithin-cholesterol acyltransferase in transgenic mice. Effect of human apolipoprotein AI and human apolipoprotein all on plasma lipoprotein cholesterol metabolism.
Human (Hu) lecithin-cholesterol acyltransferase (LCAT) is a key enzyme in the plasma metabolism of cholesterol. To assess the effects of increased plasma levels of LCAT, four lines of transgenic mice were created expressing a Hu LCAT gene driven by either its natural or the mouse albumin enhancer promoter. Plasma LCAT activity increased from 1.2- to 1.6-fold higher than that found in control mouse plasma. Lipid profiles, upon comparing Hu LCAT transgenics to control animals, revealed a 20 t0 60% increase in total and cholesteryl esters that were mainly present in HDL. The in vivo substrate specificity of Hu LCAT was assessed by creating animals expressing Hu apo AI + Hu LCAT (HuAI/ LCAT), Hu apo AI + Hu apo AII + Hu LCAT (HuAI/ AII/LCAT), and Hu apo AII + Hu LCAT (HuAII/LCAT). Plasma cholesterol was increased up to 4.2-fold in HuAI/ LCAT transgenic mice and twofold in the HuAI/AII/LCAT transgenic mice, compared with HuAI and HuAI/AII transgenic mice. HDL cholesteryl ester levels were increased more than twofold in both the HuAI/LCAT and HuAI/AII/LCAT mice compared with the HuAI, HuAI/AII, and HuLCAT animals. The HDL particles were predominantly larger in the HuAI/LCAT and the HuAI/AII/LCAT mice compared with those in HuAI, HuAII/LCAT, and HuLCAT animals. The increase in LCAT activity in the HuAI/LCAT and HuAI/AII/LCAT mice was associated with 62 and 27% reductions respectively, in the proportion of Hu apo AI in the pre beta-HDL fraction, when compared with HuAI and HuAI/AII transgenic mice. These data demonstrate that moderate increases in LCAT activity are associated with significant changes in lipoprotein cholesterol levels and that Hu LCAT has a significant preference for HDL containing Hu apo AI.
Francone
O L
OL
Cardiovascular Research Institute, University of California Medical Center, San Francisco 94143, USA.
Gong
E L
EL
Ng
D S
DS
Fielding
C J
CJ
Rubin
E M
EM
D000818:Animals; D016632:Apolipoprotein A-I / Q000096:biosynthesis / Q000378:metabolism*; D016633:Apolipoprotein A-II / Q000096:biosynthesis / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D002784:Cholesterol / Q000097:blood; D004742:Enhancer Elements, Genetic; D005260:Female; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D008074:Lipoproteins / Q000097:blood; D008099:Liver / Q000201:enzymology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D010743:Phospholipids / Q000097:blood; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013379:Substrate Specificity; D014280:Triglycerides / Q000097:blood
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D008074:Lipoproteins; D010743:Phospholipids; D011994:Recombinant Proteins; D014280:Triglycerides; D002784:Cholesterol; D015500:Chloramphenicol O-Acetyltransferase; D007862:Phosphatidylcholine-Sterol O-Acyltransferase