Funciona el tejido adiposo marrón como un depósito de acidos grasos poliinsaturados de cadena larga durante el desarrollo postnatal del cerebro? / [Is brown adipose tissue a store of long chain polyunsaturated fatty acids during postnatal developing brain?]

Mammals along their early postnatal period develop a substantial amount of a very active brown adipose tissue (BAT). Through this work we explored the possibility that BAT may function as a long chain polyunsaturated fatty acids reservoir (LC-PUFA) during the rapid growth of brain structures. In new born rats 1, 6, 12 and 20 days old, we analyzed fatty acid percentage of triglycerides (TG) and phospholipid fractions, and the absolute amount of TG. In 6 day old rats we also evaluated the extend of further desaturation of 1-14C linoleic acid administered by intraperitoneal injection. Results demonstrated a drastic increase of TG concentration during experimental period (1,5; 40; 118; 120 mg/g wet weight) and LC-PUFA percentage was higher in [quot ]1 and 6[quot ] than [quot ]12 and 20[quot ] days old rats (16-17% vs 5%). Our results showed that BAT stored important amounts of LC-PUFA. On the other hand, 1-14C linoleic acid incorporation was higher in liver than BAT. In contrast, the desaturated products of 1-14C linoleic acid /1-14C linoleic acid ratio was greater in BAT than liver (>4). This could indicate that BAT synthesizes LC-PUFA in addition to store it. In summary we demonstrated than BAT is an important reservoir of LC-PUFA during postnatal brain growth.

Los mamíferos como el hombre y la rata, poseen durante su desarrollo postnatal temprano un tejido adiposo marrón (TAM) muy activo. En este trabajo se exploró la posibilidad de que el TAM funcione como un depósito de ácidos grasos poliinsaturados de cadena larga (AGPI-CL), durante el período de máximo crecimiento postnatal del cerebro de rata. En el TAM de ratas de 1, 6, 12 y 20 días de edad analizamos la concentración de triglicéridos (TG) y la composición de ácidos grasos en los TG y fosfolípidos (FL). Además, en ratas de 6 días de edad evaluamos la capacidad del TAM para desaturar 1- 14C ácido linoleico administrado por vía intraperitoneal. Los resultados mostraron un rápido incremento en la concentración de TG durante el período experimental (1,5; 40; 118; 120 mg /g de peso húmedo). El porcentaje de AGPI-CL fue mayor en las ratas de 1 y 6 días de edad que en las de 12 y 20 días (16-17% vs 5%). Por otra parte, la incorporación de 1-14C ácido linoleico fue más alta en el hígado que en el TAM, aunque la relación "productos desaturados de 1-14C ácido linoleico / 1-14C ácido linoleico" fue mayor en el TAM que en el hígado (>4), lo cual podría indicar que este tejido además de almacenar AGPI-CL los sintetiza. En resumen, nuestros resultados demuestran que el TAM es depósito importante de AGPICL durante el período de máximo desarrollo postnatal del cerebro.

Cambios en la composición lipídica de las membranas mitocondriales de corazón de ratas inducidos por la ingesta de aceite de pescado y su relación con la actividad mitocondrial / Changes in the lipid composition of the mitochondrial membrane of the heart rat induced by fish oil intake and its relation with mitochondrial activity

Los cambios en la composición lipídica del corazón inducidos por la dieta han sido implicados en las alteraciones de la función cardíaca. El consumo de aceite de pescado, por otra parte, ha sido relacionado con la baja incidencia de enfermedades cardiovasculares. La actividad de las mitocondrias aisladas de corazones insuficientes es menor que la observada en mitocondrias de corazones normales. En este trabajo, la administración de aceite de pescado en la dieta disminuyó el contenido de C18:2n-6 y C20:4n-6 y aumentó el de C22:6n-3 en las mitocondrias de corazón. La ingesta de aceite de pescado incrementó las velocidades de respiración en estados 3 y 4 (VR3 y VR4) sin modificar la eficiencia de fosforilación ni el índice de control respiratorio. Se discute acerca de que el posible efecto protector de los ácidos grasos poli-insaturados contra los radicales libres sea ejercido a través del aumento de VR3 y VR4

[The liver as a source of essential long chain polyunsaturated fatty acids for postnatal brain development in the rat]. / Participación del hígado en el suministro de ácidos grasos esenciales poliinsaturados de cadena larga durante el desarrollo postnatal del cerebro de rata.

We address here the issue concerning the origin of essential long chain polyunsaturated fatty acids (LC-PUFA) needed for early postnatal brain development. Normal newborn rats 1, 5, 10 and 20 day-old were decapitated, immediately after, the livers were processed to obtain the microsomal fraction and its delta 6 fatty acid desaturase activity and fatty acid composition were determined. Samples of plasma, whole homogenized brain hemispheres and milk contained in the gastric cavity of the suckling rats, were analyzed to obtained their fatty acid composition. We fond that the rat neonate has a very low delta 6 desaturase activity in liver microsomes as compared with the adult. In contrast, there is a considerable quantity of DHA an AA in the milk, liver microsomes, plasma lipids and brain. In conclusion, we propose that brain DHA and AA cannot be derived substantially through liver synthesis, but through the availability of these preformed fatty acids in the milk. These fatty acids are concentrated in liver microsomes and then secreted into plasma lipid pool to reach finally to brain structures.

Changes produced by experimental hypothyroidism in fibre type composition and mitochondrial properties of rat slow and fast twitch muscles.

Experimental hypothyroidism changes the fibre type percentual composition of soleus and extensor digitorum longus muscles of rat. In both cases it has been observed an increase in the type I and a decrease in the type II fibre percentages. A reduction of proton passive permeability of mitochondrial membrane is observed in experimental hypothyroidism together with a decrease in the docosahexaenoic acid content of the mitochondrial total lipids. This change in the lipid composition could produce the reduction of the mitochondrial membrane proton passive permeability and thus, reduces state 4 mitochondrial respiratory rate of rat skeletal muscles.

Regulation of energy metabolism in Trypanosoma (Schizotrypanum) cruzi epimastigotes. II. NAD+-dependent glutamate dehydrogenase.

Trypanosoma (Schizotrypanum) cruzi epimastigotes (EP stock) grown in complex LIT medium rapidly consume the glucose present but, under aerobic conditions, continue growth in its absence with the concomitant excretion of ammonia, suggesting the utilization of amino acids for energy production. A search for metabolic pathways responsible for amino acid oxidation led to the detection of a NAD+-dependent glutamate dehydrogenase (L-glutamate:NAD+ oxidoreductase, E.C.1.4.1.2) which is different from an NADP+-dependent enzyme previously reported. The enzyme has been partially purified and its kinetic and regulatory properties studied in both directions of the reaction. Km values were 3.6 mM for alpha-ketoglutarate, 0.170 mM for NADH and 16 mM for NH+4, Vmax = 0.67 mumol min-1/mg-1 protein for aminative reduction; Km values were 23.5 mM for L-glutamate and 2.9 mM for NAD+, Vmax = 0.02 mumol min-1 mg-1 protein for deaminative oxidation, Tris buffer, pH 7.6. The enzyme is strongly inhibited by ATP, GTP, ADP and GDP (50% inhibition at 0.75 mM ATP, 3 mM MgCl2). S-Acetyl-CoA is also a potent inhibitor of the enzyme. The results demonstrate the presence of a specific pathway for the oxidation of amino acids, which is tightly regulated by the energy charge and the Krebs cycle activity in T. cruzi epimastigotes.