Lack of induction of VLDL apoprotein synthesis by medium chain fatty acids in the isolated rat liver.
Long chain fatty acids (greater than C16) are known to induce the liver synthesis of very low density lipoprotein (VLDL) apoproteins. Since medium chain (less than C16) triglycerides are used as dietary fats and in parenteral nutrition, we have investigated the relative uptake, esterification and oxidation of 14C-labelled fatty acids of a chain length of C10-C14 by the perfused rat liver compared to palmitic acid at two different concentrations: tracer (control) and overload (200 or 600 mumol/200 ml perfusate). The effect on VLDL apoprotein synthesis was simultaneously estimated by 3H-leucine incorporation. The results show: (1) a rapid liver uptake of all fatty acids; (2) a substantial incorporation into liver lipids of C12-C14 and C16, and (3) 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 in spite of their utilisation for liver and VLDL lipid synthesis. Possible explanations for these differences are discussed.
D000818:Animals; D001053:Apolipoproteins / Q000096:biosynthesis*; D005227:Fatty Acids / Q000494:pharmacology*; D066298:In Vitro Techniques; D008079:Lipoproteins, VLDL / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
D001053:Apolipoproteins; D005227:Fatty Acids; D008079:Lipoproteins, VLDL