1. Investigación

To determine whether the composition of long-chain polyunsaturated fatty acids (PUFA) could be modified in the fetus by maternal dietary fatty acids, pregnant Sprague-Dawley rats were fed semi purified diets that differed only in the non-vitamin lipid component. The diets contained either 10 g palm, sunflower, olive or fish oil (FOD)/100 g diet. A total of 5-6 rats were studied in each group. At day 20 of gestation, corresponding to 1.5 days prior parturition, the fatty acids in maternal adipose tissue were closely related to the fatty acid composition in the corresponding diet. An important proportion of arachidonic acid (AA) appeared in maternal liver and plasma, although it was lower in the FOD than in the other groups. Except for saturated fatty acids, the proportion of individual fatty acids in the placenta correlated linearly with that in maternal plasma. Also, PUFA in fetal plasma and liver showed significant correlations with PUFA in maternal plasma. Again, AA showed the lowest proportion in the plasma and liver of the FOD group. Therefore, the maternal dietary fatty acid composition influences maternal and fetal plasma and tissue composition, and an increase in dietary co-3 fatty acids decreases the amount of AA in maternal and fetal tissues.

Se ha administrado una dieta semisintética conteniendo un 10% de aceite de oliva o de pescado como único componente graso no-vitamínico a ratas preñadas, que fueron estudiadas al día 20 de gestación. En plasma de las madres, los porcentajes de ácidos grasos saturados fueron similares en ambos grupos, el de ácido oleico y de ácido araquidónico fueron superiores en las de aceite de oliva, mientras que los de ácidos eicosapentaenoico y docosahexaenoico fueron superiores en las de aceite de pescado. En el plasma de los fetos, los cambios fueron similares a los de las madres, mostrando una insuficiencia de ácido araquidónico en los de madres alimentadas con aceite de pescado. Tanto en plasma como en hígado de los fetos, la concentración de vitamina E fué inferior en los de madres alimentadas con dieta de aceite de pescado que con la de aceite de oliva. A su vez, la respuesta lipolítica de los adipocitos a un agonista b3-adrenérgico fue inferior en ratas preñadas que en vírgenes, pero el efecto inhibidor que produce en éstas el anclaje euglucémico e hiperinsulinémico desaparece cuando son alimentadas con dieta de aceite de pescado. Estos resultados muestran que un exceso en ácidos grasos poliinsaturados en la dieta durante la gestación en la rata, como el producido cuando ésta contiene aceite de pescado en vez de aceite de oliva, da lugar a una deficiencia en ácido araquidónico y vitamina E en los fetos y altera la normal respuesta lipolítica del tejido adiposo de la madre, teniendo consecuencias que podrían ser indeseables para el desarrollo postnatal.

By using different experimental designs in the rat we have been able to answer several unanswered questions on the short- and long-term effects of alterations of lipid metabolism during the perinatal stage. The first was to demonstrate the importance of maternal body fat accumulation during the first half of pregnancy, since undernutrition in this critical period when fetal growth is slow, impedes fat depot accumulation and not only restrains intrauterine development but has long-term consequences, as shown by an impaired glucose tolerance when adults. Secondly, undernutrition during suckling has major long-term effect of decreasing body weight, even though food intake is kept normal from the weaning period. Our findings also show that a diet rich in n-3 fatty acids during pregnancy and lactation has adverse effects on offspring development, but cross fostered experiments showed that this effect was a consequence of the intake of these fatty acids during the lactation period rather than during pregnancy. Pups from dams that were fed a fish oil-rich diet during pregnancy and lactation were found to have altered glucose/insulin relationship at the age of 10 weeks. Since a n-3 fatty acid-rich diet decreases milk yield during lactation, additional experiments were carried out to determine whether decreased food intake or altered dietary fatty acid composition, or both, were responsible for the long-term effects on the glucose/insulin axis. Results show that the decreased food intake caused by a n-3 fatty acidrich diet rather than the change in milk composition during suckling was responsible for the reduced pancreatic glucose responsiveness to insulin release at 16 weeks of age. In conclusion, present findings indicate that impaired maternal fat accumulation during early pregnancy and food intake during lactation, rather than a difference in dietary fatty acid composition, have major effects on postnatal development and affect glucose/insulin relationships in adult rats.

During late gestation, although maternal adipose tissue lipolytic activity becomes enhanced, lipolytic products cross the placenta with dif®culty. Under fasting conditions, free fatty acids (FFA) are used for ketogenesis by the mother, and ketone bodies are used as fuels and lipogenic substrates by the fetus. Maternal glycerol is preferentially used for glucose synthesis, saving other gluconeogenic substrates, like amino acids, for fetal growth. Placental transfer of triglycerides is null, but essential fatty acids derived from maternal diet, which are transported as triglycerides in lipoproteins, become available to the fetus owing to the presence of both lipoprotein receptors and lipase activities in the placenta. Diabetes in pregnancy promotes lipid transfer to the fetus by increasing the maternal±fetal gradient, which may contribute to an increase in body fat mass in newborns of diabetic women. Deposition of fat stores in the fetus is very low in the rat but high in humans, where body fat accretion occurs essentially during the last trimester of intra-uterine life. This is sustained by the intense placental transfer of glucose and by its use as a lipogenic substrate, as well as by the placental transfer of fatty acids and to their low oxidation activity. During the perinatal period an active ketonemia develops, which is maintained in the suckling newborn by several factors: (i) the high-fat and low-carbohydrate content in milk, (ii) the enhanced lipolytic activity occurring during the ®rst few hours of life, and (iii) both the uptake of circulating triglycerides by the liver due to the induction of lipoprotein lipase (LPL) activity in this organ, and the presence of ketogenic activity in the intestinal mucose. Changes in LPL activity, lipogenesis and lipolysis contribute to the sequential steps of adipocyte hyperplasia and hypertrophia occurring during the extra-uterine white adipose tissue development in rat, and this may be used as a model to extrapolate the intra-uterine adipose tissue development in other species, including humans.

Fundamento y objetivo. El desarrollo fetal requiere un adecuado aporte de ácidos grasos esenciales y de sus derivados de cadena larga. El objetivo de este estudio ha sido determinar en la rata preñada cómo los ácidos grasos esenciales derivados de la dieta son transportados en el plasma materno y de qué forma influyen las variaciones en la composición de los de la dieta sobre el perfil de ácidos grasos en el plasma fetal. Métodos. Desde el inicio de la gestación, las ratas fueron alimentadas con dietas semisintéticas e isocalóricas que contenían como único componente graso no vitamínico un 10% de grasa de palma, aceite de girasol, aceite de oliva o aceite de pescado. Los animales se estudiaron al día 20 de gestación y fueron alimentados ad libitum con la correspondiente dieta. Resultados. Con los cuatro tipos de dietas, los ácidos grasos poliinsaturados se encontraban en plasma preferentemente esterificados y asociados a las distintas lipoproteínas circulantes, y en particular en los triglicéridos de las de densidad < 1,006 y en los fosfolípidos de lipoproteínas de alta densidad, en vez de en forma de ácidos grasos libres. Las diferencias entre los grupos en los ácidos grasos del plasma fetal se asemejan a los del plasma materno, incluida una reducción en la proporción de ácido araquidónico en las ratas alimentadas con la dieta de aceite de pescado con relación a los demás grupos. La proporción de cada uno de los ácidos grasos poliinsaturados en plasma materno se correlacionó linealmente con los del feto, mientras que esto no ocurrió con los ácidos grasos saturados o con el ácido oleico. Conclusión. En la rata gestante, los ácidos grasos poliinsaturados del plasma se transportan preferentemente en los triglicéridos de las lipoproteínas de densidad < 1,006, varían en función de los de la dieta, y determinan los que llegan al feto. A su vez, la dieta de aceite de pescado, rica en ácidos grasos de la serie 0>-3, reduce la proporción de ácido araquidónico, lo cual puede tener consecuencias negativas en el desarrollo posnatal.

During pregnancy, lipid metabolism plays a major role to warrant the availability of substrates to the foetus. By using different experimental designs in the rat we have been able to answer several questions that were open about the short- and long-term effects of alterations of lipid metabolism during the perinatal stage. The first one was to demonstrate the importance of maternal body fat depot accumulation during the first half of pregnancy. We found that conditions like undernutrition circumscribed to this specific period when foetal growth is still small, that impede such fat accumulation not only restrain intrauterine development but also have long-term consequences, as shown by an impaired glucose tolerance when adults. Secondly, undernutrition during suckling has major long-term effect decreasing body weight, even though food intake was kept normal from the weaning period. Present findings also show that a diet rich in co-3 fatty acids during pregnancy and lactation has negative effects on offspring development, but cross fostered experiments showed that the effect was a consequence of the intake of these fatty acids during the lactation period rather than during pregnancy. Pups from dams that were fed a fish oil-rich diet during pregnancy and lactation were found to have altered glucose/insulin relationship at the age of 10 weeks. Since a ro-3 fatty acid-rich diet decreases milk yield during lactation, additional experiments were carried out to determine whether decreased food intake, altered dietary fatty acid composition, or both were responsible for the long-term effects on the glucose/insulin axis. Results show that the decreased food intake caused by a ro-3 fatty acid-rich diet rather than the change in milk composition during suckling was responsible for the reduced pancreatic glucose responsiveness to insulin release at 16 weeks of age. In conclusion, present findings indicate that impaired maternal fat accumulation during early pregnancy and food intake during lactation, rather than a difference in dietary fatty acid composition have a greater influence on postnatal development and affect glucose/insulin relationships in adult rats.

Con el propósito de conocer cómo cambios en la composición de ácidos grasos de la dieta afectan el perfil de ácidos grasos en plasma durante la gestación, y sus repercusiones en los fetos, en el presente trabajo hemos administrado dietas semisintéticas conteniendo aceite de palma, de oliva, de girasol o de pescado como único componente graso no-vitaminico a ratas preñadas. Los animales fueron estudiados al día 20 de gestación y de ser alimentados con la correspondiente dieta. Como cabía esperar, en la dieta de aceite de palma, los ácidos grasos más abundantes fueron los saturados, en la de oliva el ácido oleico, en la de girasol el ácido linoleico y la de aceite de pescado era la única que presentaba unas cantidades apreciables de ácidos eicosapentaenoico y docosahexaenoico. A su vez, ninguna de las dietas contenía ácido araquidónico. En el plasma de las madres, la proporción de ácidos grasos saturados era similar en todos los grupos, el ácido oleico era más abundante en las de dieta de palma y de oliva que en las de girasol y pescado, mientras que el ácido Iinoleico era considerablemente más alto en las de dieta de girasol. A su vez, aunque se observó una determinada proporción de ácido araquidónico en todos los grupos, su proporción era más baja en las ratas a dieta de pescado, mientras que en estas mismas ratas a dieta de pescado la proporción de ácidos eicosapentaenoico y docosahexaenoico era superior que en las otras. El perfil de ácidos grasos saturados y monoinsaturados en plasma de los fetos difiere del de sus madres, mientras que los cambios en el resto de los ácidos grasos estudiados eran similares a los de las madres, existiendo una correlación lineal y significativa en los valores de ácidos poliinsaturados entre el plasma materno y fetal. Los fetos de las ratas alimentadas con dieta de pescado presentan una intensa deficiencia en ácido araquidónico, lo que podría tener consecuencias negativas en el desarrollo postnatal.

The effect of dietary olive oil and fish oil on the lipolytic dose-response of the lh-adrenergic agonists, epinephrine, isoproterenol, BRL-37344, and CGP-12177, in adipocytes was studied in pregnant and virgin rats either untreated or under hyperinsulinemic-euglycemic conditions. Rats were fed a semisynthetic diet containing 5% of either olive oil or fish oil and studied at day 20 of treatment and/or gestation. Plasma glucose was lower and plasma insulin, triglycerides, and free fatty acids (FFAs) were higher in pregnant versus virgin rats, and the insulin sensitivity index was lower in the former. Lumbar adipose tissue phospholipid fatty acids showed a significantly higher monounsaturated fatty acid and a lower (n - 3) fatty acid content in rats fed the olive oil diet versus the fish oil diet. The lipolytic dose-response curve of either adrenergic agent was always lower in adipocytes from untreated pregnant rats versus virgin rats, and whereas the hyperinsulinemic-euglycemic clamp decreased these responses in adipocytes from virgin rats fed the olive oil diet only, adipocytes from pregnant rats always showed a decreased dose-response lipolytic curve. Thus, the lipolytic responsiveness of lh-adrenoceptor (13rAR) agonists by adipocytes is impaired in cells from rats made hyperinsulinemic chronically by pregnancy or acutely by the hyperinsulinemic-euglycemic clamp, but such response to the acute condition disappears when the adipocyte phospholipid composition is modified by changes in dietary fatty acids.

Objective: To study the changes of plasma fatty acids and lipophilic vitamins during normal pregnancy. Design: Plasma fatty acid profile and the concentration of carotenoids, tocopherols and retinol were measured in healthy women at the first and third trimesters of pregnancy, at delivery, and in cord blood plasma. Results: Maternal plasma cholesterol and triglycerides increased from the first to the third trimester of gestation, while free fatty acids progressively increased from the first trimester through the third trimester to delivery, suggesting an enhanced lipolytic activity. Plasma levels of a- and g-tocopherols, lycopene and b-carotene also progressively increased with gestation, but values in cord blood plasma were lower than in mothers at delivery. Retinol levels declined with gestational time and values in cord blood plasma were even lower. The proportion of total saturated fatty acids increased with gestation, and it further increased in cord blood plasma. Total n-9 fatty acids remained stable throughout pregnancy, and slightly declined in cord blood plasma, the change mainly corresponding to oleic acid. Total n-6 fatty acids declined with gestation and further decreased in cord blood plasma, and a similar trend was found for linoleic acid. However, arachidonic acid declined in women at the third trimester and at delivery as compared to the first trimester, but was enhanced in cord blood plasma. The proportion of total n-3 fatty acids remained stable throughout pregnancy at the expense of decreased a-linolenic acid at delivery but enhanced eicosapentaenoic acid, with small changes in docosahexaenoic acid. The proportion of these n-3 fatty acids was similar in cord blood plasma and maternal plasma at delivery. Conclusions: Owing to the different placental transfer mechanisms and fetal capability to metabolize some of the transferred fatty acids and lipophilic vitamins, the fetus preserves the essential compounds to assure their appropriate availability to sustain its normal development and to protect itself from the oxidative stress of extrauterine life. Sponsorship: The studies reported herein have been carried out with financial support from the Commission of the European Communities, specific RTD programme ‘Quality of Life and Management of Living Resources’, QLK1-2001-00138 ‘Influence of Dietary Fatty Acids on the Pathophysiology of Intrauterine Foetal Growth and Neonatal Development’ (PeriLip). It does not necessarily reflect its views and in no way anticipates the Commission’s future policy in this area.