Effect of a cholesterol-rich diet on the metabolism of the free and esterified cholesterol components of a nanoemulsion that resembles LDL in rabbits

We have shown that the free cholesterol (FC) and the cholesteryl ester (CE) moieties of a nanoemulsion with lipidic structure resembling low-density lipoproteins show distinct metabolic fate in subjects and that this may be related to the presence of dyslipidemia and atherosclerosis. The question was raised whether induction of hyperlipidemia and atherosclerosis in rabbits would affect the metabolic behavior of the two cholesterol forms. Male New Zealand rabbits aged 4-5 months were allocated to a control group (N = 17) fed regular chow and to a 1 percent cholesterol-fed group (N = 13) during a 2-month period. Subsequently, the nanoemulsion labeled with ³H-FC and 14C-CE was injected intravenously for the determination of plasma kinetics and tissue uptake of the radioactive labels. In controls, FC and CE had similar plasma kinetics (fractional clearance rate, FCR = 0.234 ± 0.056 and 0.170 ± 0.038 h-1, respectively; P = 0.065). In cholesterol-fed rabbits, the clearance of both labels was delayed and, as a remarkable feature, FC-FCR (0.089 ± 0.033 h-1) was considerably greater than CE-FCR (0.046 ± 0.010 h-1; P = 0.026). In the liver, the major nanoemulsion uptake site, uptake of the labels was similar in control animals (FC = 0.2256 ± 0.1475 and CE = 0.2135 ± 0.1580 percent/g) but in cholesterol-fed animals FC uptake (0.0890 ± 0.0319 percent/g) was greater than CE uptake (0.0595 ± 0.0207 percent/g; P < 0.05). Therefore, whereas in controls, FC and CE have similar metabolism, the induction of dyslipidemia and atherosclerosis resulted in dissociation of the two forms of cholesterol.

Influencia de la hipertrigliceridemia en el transporte reverso del colesterol / Influence of hypertriglyceridemia on reverse cholesterol transport

El transporte reverso del colesterol es la ruta metabólica por medio de la cual el colesterol excedente de los tejidos periféricos es conducido hacia el hígado para ser catabolizado. Mediante su participación en este proceso, las lipoproteínas de alta densidad (HDL) y sus subespecies constituyen las fracciones antiaterogénicas por excelencia. No obstante, esta capacidad protectora se ve deteriorada en ciertas condiciones patológicas como la hipertrigliceridemia. No sólo los niveles plasmáticos, sino también las funciones metabólicas de las HDL son afectadas por la hipertrigliceridemia. De esta manera, la hipertrigliceridemia influye sobre cada una de las etapas del transporte reverso del colesterol: 1) eflujo de colesterol libre desde la membrana celular y captación por la preß1-HDL; 2) esterificación del colesterol libre por la lecitina: colesterol aciltransferasa; 3) transferencia del colestrol esterificado hacia lipoproteínas que contienen apo B por la proteína transportadora de colesterol esterificado; y 4) remoción del colesterol esterificado de la circulación plasmática por el hígado. Particularmente, se evidenciaron modificaciones en las características fisicoquímicas y funcionales de las lipoproteínas aceptoras del eflujo de colesterol libre de las membranas celulares. Las anormalidades en el transporte reverso del colesterol, causadas por la hipertrigliceridemia, contribuirían a la hipótesis que asocia a la elevación de las concentraciones plasmáticas de triglicéridos con la aterosclerosis

Effect of oryzanol on cholesterol absorption & biliary & fecal bile acids in rats.

Effect of oryzanol on biliary secretion of cholesterol, phospholipid and bile acids and fecal excretion of cholesterol and bile acids was examined in male albino rats. Feeding oryzanol at 0.5 per cent level with the control diet did not cause any change in bile flow and composition. On feeding oryzanol with high cholesterol diet, the bile flow and total bile acid output were increased by 12 and 18 per cent respectively, while biliary cholesterol and phospholipids remained unchanged. The increased bile acid secretion was mainly due to taurocholic acid. In rats fed oryzanol along with high cholesterol diet, there was a significant increase in the fecal excretion of cholesterol (28%) and of bile acids (29%), whereas cholesterol absorption was lowered by 20 per cent.