TAILIEUCHUNG - Báo cáo Y học: Structural and compositional changes in very low density lipoprotein triacylglycerols during basal lipolysis

Triacylglycerols secreted by liver and carried by very low density lipoprotein (VLDL) are hydrolysed in circulation by lipoprotein and hepatic lipases. These enzymes have been shown to have positional and fatty acid specificityin there were specificity in basal lipolysisin vivo, triacylglycerol compositionsofcirculatingandnewlysecretedVLDLwould be different. To study this we compared the composition of normal fasting VLDL triacylglycerol of Wistar rats to that obtained after blocking lipolysis by Triton WR1339, which increasedplasmaVLDL triacylglycerol concentrationabout in 2 h. . | Eur. J. Biochem. 269 6223-6232 2002 FEBS 2002 doi Structural and compositional changes in very low density lipoprotein triacylglycerols during basal lipolysis Jyrki J. Agren1 2 Amir Ravandi1 Arnis Kuksis1 and George Steiner3 1 Banting and Best Department of Medical Research University of Toronto Ontario Canada department of Physiology University of Kuopio Finland 3Department of Medicine and Physiology The Toronto Hospital General Division Toronto Ontario Canada Triacylglycerols secreted by liver and carried by very low density lipoprotein VLDL are hydrolysed in circulation by lipoprotein and hepatic lipases. These enzymes have been shown to have positional and fatty acid specificity in vitro. If there were specificity in basal lipolysis in vivo triacylglycerol compositions ofcirculating and newly secreted VLDL would be different. To study this we compared the composition of normal fasting VLDL triacylglycerol of Wistar rats to that obtained after blocking lipolysis by Triton WR1339 which increased plasma VLDL triacylglycerol concentration about in 2 h. Analyses of molecular species of sn-1 2- and sn-2 3-diacylglycerol moieties and stereospecific triacylglycerol analysis revealed major differences between the groups in the VLDL triacylglycerol composition. In nontreated rats the proportion of16 0 was higher and that ofl 8 2n-6 lowerin the sn-1 position. The proportion of 14 0 was kweer m all positions and that of 18 0 was L wr m the sn-1 and sn-3 positions in nontreated rats whereas the proportions of 20 4n-6 20 5n-3 22 5n-3 and 22 6n-3 were higher in the sn-1 and lower in the sn-2 position. These results suggest that the fatty acid of the sn-1 position is the most decisive factor in determining the sensitivity for hydrolysis of the triacylglycerol. In addition triacylglycerol species with highly unsaturated fatty acids in the sn-2 position also favoured hydrolysis. The in vivo substrate specificity followed only partly that

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