Incorporation and distribution of saturated and unsaturated fatty acids into nuclear lipids of hepatic cells.
Liver nuclear incorporation of stearic (18:0), linoleic (18:2n-6), and arachidonic (20:4n-6) acids was studied by incubation in vitro of the [1-14C] fatty acids with nuclei, with or without the cytosol fraction at different times. The [1-14C] fatty acids were incorporated into the nuclei as free fatty acids in the following order: 18:0 > 20:4n-6 >> 18:2n-6, and esterified into nuclear lipids by an acyl-CoA pathway. All [1-14C] fatty acids were esterified mainly to phospholipids and triacylglycerols and in a minor proportion to diacylglycerols. Only [1-14C]18:2n-6-CoA was incorporated into cholesterol esters. The incorporation was not modified by cytosol addition. The incorporation of 20:4n-6 into nuclear phosphatidylcholine (PC) pools was also studied by incubation of liver nuclei in vitro with [1-14C]20:4n-6-CoA, and nuclear labeled PC molecular species were determined. From the 15 PC nuclear molecular species determined, five were labeled with [1-14C]20:4n-6-CoA: 18:0-20:4, 16:0-20:4, 18:1-20:4, 18:2-20:4, and 20:4-20:4. The highest specific radioactivity was found in 20:4-20:4 PC, which is a minor species. In conclusion, liver cell nuclei possess the necessary enzymes to incorporate exogenous saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver cell nuclei also utilize exogenous 20:4n-6-CoA to synthesize the major molecular species of PC with 20:4n-6 at the sn-2 position. However, the most actively synthesized is 20:4-20:4 PC, which is a quantitatively minor component. The labeling pattern of 20:4-20:4 PC would indicate that this molecular species is synthesized mainly by the de novo pathway.
Ves-Losada
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Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, UNLP-CONICET, La Plata, Argentina. avlosada@nahuel.biol.unlp.edu.ar
Maté
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Brenner
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D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002250:Carbon Radioisotopes; D002467:Cell Nucleus / Q000378:metabolism*; D002788:Cholesterol Esters / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004951:Esterification; D005227:Fatty Acids / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007700:Kinetics; D019787:Linoleic Acid / Q000378:metabolism; D050356:Lipid Metabolism; D008099:Liver / Q000648:ultrastructure*; D008297:Male; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013229:Stearic Acids / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
D002250:Carbon Radioisotopes; D002788:Cholesterol Esters; D004075:Diglycerides; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D010713:Phosphatidylcholines; D010743:Phospholipids; D013229:Stearic Acids; D014280:Triglycerides; D016718:Arachidonic Acid; C031183:stearic acid; D019787:Linoleic Acid