Document Detail

Triglyceride metabolism in 3T3-L1 cells. An in vivo 13C NMR study.
MedLine Citation:
PMID:  1317859     Owner:  NLM     Status:  MEDLINE    
13C nuclear magnetic resonance spectroscopy has been used to study triglyceride metabolism in 3T3-L1 cells incubated with [1-13/14C] acetate, myristate, palmitate, stearate, or oleate. Labeled cells embedded in agarose filaments were perfused in a specially fitted NMR tube within the spectrometer magnet. Incubation of 3T3-L1 cells with a specific fatty acid enriched the cellular triglycerides with that fatty acid; the NMR signal observed in the carbonyl region of the cell spectrum was due in large part to that fatty acid. NMR data demonstrated that cellular enzymes preferentially esterified saturated fatty acids at the glyceride sn-1,3 position and unsaturated fatty acids at the sn-2 position. cellular triglyceride hydrolysis by hormone-sensitive lipase was monitored by measuring the decrease in the integrated intensities of resonances arising from fatty acyl carbonyls esterified at glycerol carbons sn-1,3 and sn-2. Under basal conditions, the time courses were first-order, and the average rates were 0.14% of signal/min at both carbonyl positions. Under isoproterenol stimulated conditions, these rates were still first-order and increased 6.4-fold at the sn-1,3 position and 2.4-fold at the sn-2 position. The observation that the hydrolysis time courses were first-order suggested that only a small amount of cellular triglyceride was available to hormone-sensitive lipase, supporting the view that lipolytic enzymes operate at lipid surfaces where only small amounts of neutral lipid may be soluble. Attempts to correlate the measured rates with the rates of hydrolysis at the sn-1,3 and sn-2 positions were hindered by the fact that the chemical shifts of the carbonyl carbons of the diglyceride hydrolysis product did not overlie those of the triglyceride. Analysis of hydrolysis kinetics revealed that hormone-sensitive lipase exhibited little preference for a particular esterified fatty acid under basal conditions; however, under stimulated conditions, the enzyme exhibited a preference for certain triglyceride species.
M R Soma; M P Mims; M V Chari; D Rees; J D Morrisett
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  267     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1992 Jun 
Date Detail:
Created Date:  1992-07-06     Completed Date:  1992-07-06     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  11168-75     Citation Subset:  IM    
Magnetic Resonance Center, Baylor College of Medicine, Houston, Texas 77030.
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MeSH Terms
3T3 Cells
Adipose Tissue / cytology,  metabolism
Carbon Isotopes
Cyclic AMP / metabolism
Fatty Acids / metabolism
Isoproterenol / pharmacology
Magnetic Resonance Spectroscopy
Triglycerides / metabolism*
Grant Support
Reg. No./Substance:
0/Carbon Isotopes; 0/Fatty Acids; 0/Triglycerides; 60-92-4/Cyclic AMP; 7683-59-2/Isoproterenol

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