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Journal of Lipid Research, Vol. 48, 1108-1121, May 2007
Copyright © 2007 by American Society for Biochemistry and Molecular Biology
Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032
Published, JLR Papers in Press, February 3, 2007.
1 To whom correspondence should be addressed. e-mail: hng1{at}columbia.edu
Prior studies have suggested that FAs liberated in the small intestine from ingested 1,3-diacylglycerol (DAG) are inefficiently incorporated into triglyceride (TG) in enterocytes, with less chylomicron TG entering the circulation postprandially. We found less TG, but more monacylglyerol and DAG, with similar total acylglycerol in newly secreted chylomicrons after oral DAG or triacylglycerol (TAG). However, clearance of DAG-chylomicrons was more rapid than that of TAG-chylomicrons; this was associated with more efficient in vitro LPL-mediated lipolysis of DAG-derived chylomicrons. Intravenously infused DAG was also cleared faster than TAG in normal mice, via both LPL-mediated lipolysis and apolipoprotein E (apoE)-dependent hepatic uptake. Infusions of TAG, but not DAG, increased plasma TG levels. Greater delivery of DAG-derived FA to the liver during infusion of DAG led to greater TG secretion versus TAG; this allowed the maintenance of similar hepatic TG levels after DAG and TAG infusions. Of note, apoB secretion was similar after DAG versus TAG, indicating the assembly of larger very low density lipoproteins after DAG. In conclusion, reduced plasma TG levels, after oral or intravenous DAG, result from more efficient clearance of DAG by both LPL lipolysis and apoE-mediated hepatic endocytosis. DAG emulsions may by useful for intravenous nutrition in people with preexisting hypertriglyceridemia.
Supplementary key words triglycerides lipoprotein metabolism chylomicron metabolism
Abbreviations: AG, acylglycerol; AOX, acyl-coenzyme A oxidase; apoB, apolipoprotein B; CE, cholesteryl ester; CEt, cholesterol oleoyl ether; CPT-1, carnitine palmitoyltransferase-1; DAG, diacylglycerol; DO, diolein; MAG, 1-monoacylglycerol; PhP, postheparinized plasma; PPAR
, peroxisome proliferator-activated receptor
; TAG, triacylglycerol; TG, triglyceride; TO, triolein
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