Browsing by Author "Gómez Coronado, Diego"

The apolipoprotein (apo) E phenotype and its influence on plasma lipid and apolipoprotein levels were determined in men and women from a working population of Madrid, Spain. The relative frequencies of alleles i:2, d and i:4 for the study population (n = 614) were 0.080, 0.842 and 0.078, respectively. In men, apo E polymorphism was associated with variations in plasma triglyceride and very low-density lipoprotein (VLDL) lipid levels. lt was associated with the proportion of apo C-II in VLDL, and explained 5.5% of the variability in the latter parameter. In women apo E polymorphism was associated with the concentrations of plasma cholesterol and low-density Iipoprotein (LDL) and high-density lipoprotein (HDL) related variables. The allelic effects were examined taking allele c3 homozygosity as reference. In men, allele i:2 significantly increased VLDL triglyceride and VLDL cholesterol concentrations, and this was accompanied by an increase of the apo C-II content in these particles. Allele i:4 did not show any significant influence on men's lipoproteins. In women, allele i:2 lowered LDL cholesterol and apo B levels, while allele i:4 increased LDL cholesterol and decreased the concentrations of HDL cholesterol, HDL phospholipid and apo A-1. These effects were essentially maintained after excluding postmenopausal women and oral contraceptive users from the analysis. In conclusion: (1) the population of Madrid, similar to other Mediterranean populations, exhibits an underexpression of apo E4 compared to the average prevalence in Caucasians, (2) gender interacts with the effects of apo E polymorphism: in women, it influenced LDL and HDL levels, whereas in men it preferentially affected VLDL, and (3) allele i:2 decreased LDL levels in women, while it increased both VLDL lipid levels and apo C-II content in men, but, in contrast to allele i:4, it did not show an impact on HDL in either sex.

Human very-low-density lipoproteins (VLDL) were subfractionated by heparin-Sepharose chromatography into an unbound (:\I and three bound (B, C and D) populations at increasing ionic strengths. Subfractions were characterized regarding their chemic;,[ composition and efficiency of triacylglycerol hydrolysis by rat adipose tissue LPL. The triacylglycerol content decreased, whcrca, the cholesterol and protein contents increased from subfractions A and B to subfraction D. VLDL-D showed the highest ap<' E/apo C ratio, though all the subfractions contained appreciable apo E. Appearance of VLDL-A resulted from exceeding the binding capacity of the column, since practically all its particles eluted at positions of bound VLDL under re-chromatograph~ Subfractions B, C and D stimulated LPL activity on emulsified tri[ 14C]oleoylglycerol to a similar extent, indicating that their 3P'' C-11 content was equally effective activating LPL. Incubation of tri[ 14C]oleoylglycerol labeled VLDL subfractions with fat pad pieces in the presence or absence of heparin resulted in greater hydrolysis and fatty acid uptake for VLDL-B and -C than f.•1 VLDL-D, a pattern observed over a wide range of LPL activities in the media. We conclude: (1) any VLDL particle can intcr;t,1 with heparin, which is consistent with the presence of apo E in all the subfractions, and (2) triacylglycerols in apo E-rich VLDI are less efficiently hydrolyzed by LPL than those in apo E-poor particles. We propose that richness in apo E impairs LPL acu"r upon VLDL and decreases the rate of delivery of fatty acids to peripheral tissues.

On the basis of bibliographic references and new own data, major adaptations of lipid metabolism occurring at late gestation are reviewed. Maternal hypertriglyceridemia at late gestation results from the juxtaposition of several factors: ( 1) enhanced adipose tissue lipolysis facilitating the availability to the liver of substrates for triglyceride synthesis and contributing to augmented flux of very low density lipoproteins (VLDL) into the circulation; (2) maternal hyperphagia and unmodified gut lipid absorption increasing chylomicron formation from dietary lipid; (3) reduced lipoprotein lipase (LPL) activity in extrahepatic tissues (especially adipose tissue) which does not allow a triglyceride removal proportional to their enhanced production. It is proposed that these changes are also responsible for the altered composition ofVLDL in late pregnancy. In conditions of food deprivation the use of glycerol released from adipose tissue as preferential gluconeogenic substrate, and the enhanced maternal ketogenesis warrants the availability of fuels for the fetus. Just prior to parturition the increase in mammary gland LPL activity is responsible for the reduction in circulating triglycerides and prepares the mother for lactation.

Se dispone en la actualidad de una gama de técnicas analíticas y preparativas para el subfraccionamiento de las VLDL que están permitiendo el estudio de su significado funcional. El concepto de que "las VLDL transpo11an triglicéridos y se transforman en LDL o bien se aclaran directamente del plasma", aun siendo cierto es una simplificación de todo un conjunto de procesos protagonizados por diversas enzimas, apolipoproteínas, lípidos, receptores celulares y proteínas intercambiadoras, no todos ellos bien conocidos. Las distintas subpoblaciones de lipoprotcínas pueden representar eslabones de una cadena única o de varias cadenas, independientes o entrelazadas, lo cual todavía está por determinar. Pensamos que el estudio del metabolismo de subpoblaciones homogéneas contribuirá previsiblemente al esclarecimiento de la sucesión de eventos que configuran el metabolismo de las lipoproteínas transportadoras de triglicéridos.

Extraction and chromatographic conditions for measuring tocopherols from Laurus nobilis were optimized. Newly harvested leaves were dried in a microwave oven and crushed; then, R- and γ-tocopherol and tocol, added as internal standard, were directly extracted from portions of ground material with acetone, by probe sonication. After centrifugation and filtration, the acetonic extract was directly analyzed by HPLC using a gradient elution with a Discovery C18 column (25 × 0.46 cm) at 35 °C. UV and fluorescence detections were employed simultaneously. Validation parameters of the method for linearity, accuracy, and precision can be considered to be adequate for both detection modes. After validation, a number of samples selected from different geographical areas in the Iberian peninsula were measured, and results compared with those in the literature gave surprisingly high values.

En esta revisión hemos intentado poner de manifiesto el papel que desempeña la LPL en el destino de los triglicéridos circulantes, los cuales cuando son de origen endógeno (síntesis hepática de sustratos nolipídicos y/o de los productos de la lipolisis, FFA y glicerol), lo hacen asociados a las VLDL. El efecto de distintos factores o situaciones fisiolóficas sobre la actividad LPL varía de unos tejidos a otros. Así, mientras que en tejido adiposo la actividad de la enzima aumenta con la insulina y disminuye con el ayuno y la gestación, en corazón y músculo esquelético disminuye con la insulina y aumenta en situaciones de hipotrigliceridemia, con el ayuno, o por el tratamiento con glucocorticoides. En la glándula mamaria la enzima es inducida por la prolactina, y éste es el mecanismo por el que aumenta su actividad al final de la gestación. En hígado del recién nacido, la LPL se relaciona de forma inversa con los niveles de insulina, mientras que aumenta con la hipotrigliceridemia, como ocurría en la enzima de corazón, y su actividad es inhibida tras el tratamiento con insulina. A pesar de estas diferencias en la respuesta a distintos efectores, la LPL parece ser igual desde el punto de vista estructural en todos los tejidos, y no conocemos a qué se deben esas diferencias funcionales. La LPL no solamente hidroliza a los triglicéridos que circulan en plasma asociados a las lipoproteínas ricas· en ellos, quilomicrones y VLDL, sino que facilita la captación de los productos de dicha hidrólisis por el tejido subyacente, canalizando así la utilización de los mismos en el organismo. El destino metabólico de esos productos, FF A y glicerol, varía también de unos tejidos a otros. Mientras que en tejido adiposo son utilizados para su reesterificación y acúrnulo, constituyendo una importante reserva energética para el organismo, en músculo cardíaco y esquelético y en hígado del recién nacido son oxidados para su utilización como fuente inmediata de energía, en glándula mamaria se transforman en los lípidos de la leche, y en pulmón son sustratos para la síntesis del surfactani.e. Así pues, la LPL juega un papel clave en el metabolismo de las VDL y quilomicrones, tanto facilitando la transformación de estas lipoproteínas en otras de mayor densidad, que son finalmente eliminadas de la circulación, como modulando la canalizando de los triglicéridos que transportan a tejidos específicos, para su posterior metabolismo intracelular.

En esta revisión hemos intentado poner de manifiesto el papel que desempeña la LPL en el destino de los triglicéridos circulantes que, cuando son de origen endógeno (síntesis hepática de sustratos no-lipídicos y/o de los productos de la lipolisis, FFA y glicerol), lo hacen asociados a las VLDL. El efecto de distintos factores o situaciones fisiológicas sobre la actividad LPL varia de unos tejidos a otros. Así, mientras que en tejido adiposo la actividad de la enzima aumenta con la insulina y disminuye con el ayuno y la gestación, en corazón y músculo esquelético disminuye con la insulina y aumenta en situaciones de hipotrigliceridemia, con el ayuno, o por el tratamiento con glucocorticoides. En la glándula mamari3 la enzima es inducida por la prolactina, y éste es el mecanismo por el que aumenta su actividad al final de la gestación. En hígado de recién nacido, la LPL se relaciona de forma inversa con los niveles de insulina, mientras que aumenta con la hipotrigliceridemia, como ocurría en la enzima de corazón, y su actividad es inhibida tras el tratamiento con insulina. A pesar de estas diferencias en la respuesta a distintos efectores, la LPL parece ser igual des de el punto de vista estructural en todos los tejidos, y no conocemos a qué se deben esas diferencias funcionales. La LPL no solamente hidroliza a los triglicéridos que circulan en plasma asociados a las lipoproteínas ricas en ellos, quilomicrones y VLDL, sino que facilita la captación de los productos de dicha hidrólisis por el tejido subyacente, canalizando así la utilización de los mismos en el organismo. El destino metabólico de esos productos, FFA y glicerol, varía también de unos tejidos a otros. Mientras que en tejido adiposo son utilizados para su reesterificación y acúmulo, constituyendo una importante reserva energética para el organismo, en músculo cardíaco y esquelético y en hígado de recién nacido son oxidados para su utilización como fuente inmediata de energía; en glándula mamaria se transforman en los lípidos de la leche, y en pulmón son sustratos para la síntesis del tensioactivo. Así pues, la LPL juega un papel clave en el metabolismo de las VLDL y quilomicrones, tanto facilitando la transformación de estas lipoproteínas en otras de mayor densidad, que son finalmente eliminadas de la circulación, como modulando la canalización de 1011 triglicéridos que transportan a tejidos específicos, para su posterior metabolismo intracelular.

The mechanism that induces maternal hypertriglyceridemia in late normal pregnancy, and its physiologic significance are reviewed as a model of the effects of sex steroids on lipoprotein metabolism. In the pregnant rat, maternal carcass fat content progressively increases up to day 19 of gestation, then declines at day 21. The decline may be explained by the augmented lipolytic activity in adipose tissue that is seen in late pregnancy in the rat. This change causes maternal circulating free fatty acids and glycerol levels to rise. Although the liver is the main receptor organ for these metabolites, liver triglyceride content is reduced. Circulating triglycerides and very-low-density lipoprotein (VLDL)-triglyceride levels are highly augmented in the pregnant rat, indicating that liver-synthesized triglycerides are rapidly released into the circulation. Similar increments in circulating VLDL-triglycerides are seen in pregnant women during the third trimester of gestation. This increase is coincident with a decrease in plasma postheparin lipoprotein lipase activity, indicating a reduced removal of circulating triglycerides by maternal tissues or a redistribution in their use among the different tissues. During late gestation in the rat, tissue lipoprotein lipase activity varies in different directions; it decreases in adipose tissue, the liver, and to a smaller extent the heart, but increases in placental and mammary gland tissue. These changes play an important role in the fate of circulating triglycerides, which are diverted from uptake by adipose tissue to uptake by the mammary gland for milk synthesis, and probably by the placenta for hydrolysis and transfer of released nonesterified fatty acids to the fetus. After 24 hours of starvation, lipoprotein lipase activity in the liver greatly increases in the rat in late pregnancy; this change is not seen in virgin animals. This alteration is similar to that seen in liver triglyceride content and plasma ketone body concentration in the fasted pregnant rat. In the fasting condition during late gestation, heightened lipoprotein lipase activity is the proposed mechanism through which the liver becomes an acceptor of circulating triglycerides, allowing their use as ketogenic substrates, so that both maternal and fetal tissues may indirectly benefit from maternal hypertriglyceridemia. Changes in the magnitude and direction of lipoprotein lipase activity in different tissues during gestation actively contribute both to the development of hypertriglyceridemia and to the metabolic fate of circulating triglycerides. Any deviation in these metabolic adaptations occurring in the human mother may have consequences that modify her lipoprotein profile, even postpartum. Hormone-induced changes in pregnancy mirror those seen with oral contraceptive steroids and provide a teleologic rationale for the lipoprotein changes induced by sex steroids.

Since natural antioxidants present increasing interest for food industry due to their beneficial effect on health, new potential sources have been screened among edible aromatic plants and a microalgae, Spirulina platensis. The determination was performed after optimising a previously validated method, because important differences have been found among values described in literature for tocopherol content in products of vegetable origin. Values obtained ranged from 3.42 mg -tocopherol/100 g of dill to 132.2 mg/100 g of fresh bay and from 0.14 mg -tocopherol/100 g of spearmint to 3.45 mg/100 g of parsley. In all cases results were calculated from fresh leaves. Preliminary experiments were developed with bay (Laurus nobilis) plant to devise the supercritical fluid extraction of tocopherols, generating environmentally friendly processes to selectively extract fractions enriched with antioxidant compounds while removing fractions corresponding to essential oils, that is, those that correspond to the characteristic aroma of the plants. Another striking result has been the tocopherol content in the microalgae, 1.3 mg -tocopherol/100 g of dried commercial spirulina, which do not justify the supposed source of antioxidant vitamins. Results suggest the need of more reliable determinations of tocopherols in vegetable sources to be included in databases.