Influencia de la composición en ácidos grasos de los remanentes de quilomicrones derivados de aceite de pescado o de maíz en el perfil lipídico de los hepatocitos de rata en cultivo

Abstract

The aim of this work was to characterise the lipid and fatty acid composition of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) and to investigate their influence on the fatty acid profiles of the lipids of rat hepatocytes cultured in monolayers. Chylomicrons were prepared from the lymph collected from the thoracic duct of rats given an oral dose of fish or corn oil (high in n-3 and n-6 PUFA, respectively), and remnants were prepared in vitro from such chylomicrons using rat plasma containing lipoprotein lipase. The fatty acids predominating in the oils abounded also in their respective chylomicrons and remnants, especially in triacylglycerols. Chylomicrons as well as remnants contained small amounts of phospholipids and long-chain PUFA that were minor in, or absent from, the dietary oils, evidently provided by the intestinal epithelium. The incubation of hepatocytes for 6 h, with either n-3 or n-6 PUFA-rich remnants (0.25-0.75 mM triacylglycerol) resulted in a dose-dependent increase in the amount of triacylglycerols and phospholipids in the cells, which was not affected further by increasing the incubation time to 19 h. Whereas hepatocyte triacylglycerols mostly incorporated the PUFA predominating in each remnant type, the fatty acid profile of cell phospholipids was virtually unchanged. In addition, irrespective of whether they were enriched in n-3 or n-6 PUFA, remnants promoted a relative decrease in the amount of cholesteryl esters, a minor hepatocyte lipid class poor in PUFA. The results demonstrate that the hepatocyte fatty acid profile is modulated in a lipid-class specific way by the amount and type of dietary PUFA delivered to cells in chylomicron remnants.

Effect of n-3 fatty acids on metabolism of apoB100-containing lipoprotein in type 2 diabetic subjects

“…To distinguish a chronic effect of n-3 fatty acids and an acute effect of n-3 absorption, the study was performed in the fasting state, in contrast to a previous study by Fisher et al (1998). It is well known that chylomicrons and their remnants enriched in n-3 fatty acids (Zheng et al 2001;Maldonado et al 2003) or a direct delivery of dietary n-3 PUFA to the liver (Wang et al 1993) reduces hepatic VLDL synthesis. A study design performed in the feeding state did not allow a discrimination between a short-term effect consequent on absorptive flux and a long-term effect consequent on a change in cell membrane composition.…”

“…In that study, the increase in LDL production with no change of fractional catabolic rate led to an increase in LDL mass. However, the study was conducted in feeding subjects, which implies a possible acute effect of n-3-rich chylomicrons and their remnants on apoB100 metabolism (Zheng et al 2001;Maldonado et al 2003). Moreover, in that study (Fisher et al 1998), the authors only compared the effect of n-3 to n-6 fatty acids, two acids known to influence lipid homeostasis (Mekki et al 2002;Zheng et al 2002).…”

Mechanism by which dietary polyunsaturated fat regulates lipogenic gene expression

“…that are taken up by the liver from chylomicron remnants also represent the same types of fats present in the diet (Figure 5)(258,259).…”