citrate carrier and lipogenic enzyme activities in liver subcellular fractions of safflower oil-fed animals

 G.V. Gnoni, V. Zara, A.M. Giudetti, A.M. Caputi Jambrenghi, M. Ragni, L. Zezza and G. Vonghia

 Abstract

The tricarboxylate (citrate) carrier plays an important role in hepatic lipogenesis by exporting acetyl-CoA from the mitochondrial matrix to the cytosol. Here, acetyl-CoA is the primer for the de novo fatty acid and cholesterol synthesis. In this study the effect of a fat (high linoleic (n-6) safflower oil [S.O.]) enriched diet both on lipogenic enzymes and on tricarboxylate carrier activities was investigated. Citrate transport was strongly reduced in liver mitochondria isolated from S.O.-treated rats. Kinetic analysis of the carrier activity showed that Vmax was the only parameter decreased, whereas Km was almost unaffected. Apparently, no variation in the overall fluidity of the mitochondrial membrane of S.O.-treated rats occurred in spite of some changes in membrane lipid composition and in the degree of fatty acid unsaturation. Simultaneously, a decrease of lipogenic enzyme activities, i.e. acetyl-CoA carboxylase and fatty acid synthetase, was also observed following S.O. administration. The S.O. effect on hepatic fatty acid synthesis as well as on lipid composition of some lamb tissues was also investigated. In treated lamb tissues an increase in the polyunsaturated fatty acid (PUFA) level together with a decrease in saturated fatty acid and cholesterol content were observed.

Key words:  liver mitochandria, oil-fed animals, dietary fat, Carthamus tinctorius L.