Inhibition of acylcoenzyme A:cholesterol acyltransferase activity in CaCo-2 cells results in intracellular triglyceride accumulation.
The activity of acylcoenzyme A:cholesterol acyltransferase (ACAT) in CaCo-2 cells was inhibited by the ACAT inhibitor, 58-035. The inhibitory effect of this acylamide was specific for cholesterol esterification catalyzed by ACAT; the rates of triglyceride, phospholipid, and cholesterol synthesis were not inhibited by this agent. Cholesteryl esters were depleted in CaCo-2 cells 24 hr after inhibition of ACAT activity, whereas the unesterified cholesterol content increased by 56% after 96 hr. Moreover, inhibiting ACAT activity with 58-035 resulted in a time-dependent 2.5-fold increase in intracellular triglycerides. This accumulation of triglycerides in CaCo-2 cells was associated with a 37% increase in triglyceride synthesis by 96 hr in the presence of 58-035. Triglyceride-rich lipoprotein secretion (d less than 1.006 g/ml) was not affected by inhibiting ACAT activity for up to 6 hr. However, triglyceride-rich lipoprotein secretion was significantly decreased in CaCo-2 cells that were preincubated with 58-035 for 24 to 96 hr. Lipoproteins of density less than 1.006 g/ml that were isolated from CaCo-2 cells incubated with the ACAT inhibitor were deficient in cholesteryl esters and triglycerides compared to lipoproteins isolated from control cells. The data suggest that triglycerides accumulate in CaCo-2 cells in which ACAT activity has been inhibited by 58-035. This accumulation of triglycerides is associated with a modest increase in triglyceride synthesis and a decrease in triglyceride secretion. Altering intracellular cholesterol pools by regulating ACAT activity in the gut could result in the decrease of triglyceride transport and/or the secretion of triglyceride-rich lipoprotein particles of abnormal composition.
Kam
N T
NT
Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City 52242.
Albright
E
E
Mathur
S N
SN
Field
F J
FJ
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology*; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D007422:Intestines / Q000166:cytology; D017646:Organosilicon Compounds; D002785:Sterol O-Acyltransferase / Q000378:metabolism*; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism*
D000214:Acyl Coenzyme A; D000577:Amides; D017646:Organosilicon Compounds; D014280:Triglycerides; C040256:SAN 58035; D002784:Cholesterol; D002785:Sterol O-Acyltransferase