Synthesis and secretion of apoC-I and apoE during maturation of human SW872 liposarcoma cells.
Little is known about the regulation of apolipoprotein (apo) C-I production by human adipocytes. The aim of the present study, therefore, was to investigate the effect of different tissue culture conditions on the synthesis and secretion of apoC-I and apoE in human SW872 liposarcoma cells. After 3-4 d in culture (0.5 x 10(6) cells/well, DMEM/F-12 medium with 10% fetal calf serum), cells reached confluence and became growth arrested. The molar ratio of apoE:apoC-I in the cell was 8.9 +/- 0.6 and in the medium was 6.6 +/- 0.5. After 17 d in culture, SW872 cells contained significantly more cholesterol (100%) and triglyceride (3-fold) and secreted more apoC-I [4 vs. 17 d: 0.11 +/- 0.01 vs. 0.23 +/- 0.01 pmol/(10(6) cells . 24 h), P < 0.001] and apoE [0.7 +/- 0.1 vs. 3.1 +/- 0.3 pmol/(10(6) cells . 24 h), P < 0.001]. Cellular apoC-I increased 7-fold and apoE increased 16-fold. Cell maturation was associated with significantly higher levels of apoE mRNA but not apoC-I mRNA. Increases in cell lipids, apoC-I, and apoE were not dependent on the presence of extracellular lipids because similar changes occurred in cells incubated with lipoprotein-deficient serum or in cells incubated without serum. Treatment (7 d) of cells during maturation with insulin (10 or 1000 nmol/L) significantly reduced the secretion of apoC-I and apoE. These results demonstrate that in maturing SW872 cells, cholesterol and triglyceride accumulation in the presence or absence of extracellular lipids, is associated with increased apoC-I and apoE production. Furthermore, apoC-I and apoE production are differentially regulated at the transcriptional level, and long-term treatment with insulin has an inhibitory rather than stimulatory effect on apoC-I and apoE production.
Wassef
Hanny
H
Hyperlipidemia and Atherosclerosis Research Group, Clinical Research Institute of Montréal, Montréal, Quebec, Canada.
Bernier
Lise
L
Davignon
Jean
J
Cohn
Jeffrey S
JS
D017667:Adipocytes / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D001056:Apolipoproteins C / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D001057:Apolipoproteins E / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D002784:Cholesterol / Q000378:metabolism; D003470:Culture Media; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008080:Liposarcoma; D047493:PPAR alpha / Q000235:genetics; D047495:PPAR gamma / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D014280:Triglycerides / Q000378:metabolism; D014407:Tumor Cells, Cultured
D001056:Apolipoproteins C; D001057:Apolipoproteins E; D003470:Culture Media; D007328:Insulin; D047493:PPAR alpha; D047495:PPAR gamma; D012333:RNA, Messenger; D014280:Triglycerides; D002784:Cholesterol