Lack of Induction of VLDL Apoprotein Synthesis by Medium Chain Fatty Acids in the Isolated Rat Liver

Abstract

Long chain fatty acids (> C16) induce liver synthesis of very low density lipoprotein (VLDL) apoproteins. Since medium chain (< C16) triglycerides are used as dietary fats and in parenteral nutrition, the relative uptake, esterification and oxidation of 14C-labeled fatty acids of a chain length of C10-C14 by the perfused rat liver compared to palmitic acid at 2 different concentrations: tracer (control) and overload (200 or 600 .mu.mol/200 ml perfusate) were investigated. The effect on VLDL apoprotein synthesis was simultaneously estimated by 3H-leucine incorporation. A rapid liver uptake of all fatty acids, a substantial incorporation into liver lipids of C12-C14 and C16 and a higher oxidation rate of medium chain compared to long chain fatty acids (a lack of induction of VLDL apolipoprotein by an overload of fatty acids shorter than palmitic acid despite their utilization for liver and VLDL lipid synthesis) were found. Possible explanations for these differences are discussed.