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INCORPORACION Y DISTRIBUCION DE ACIDOS GRASOS SATURADOS E INSATURADOS EN LOS LIPIDOS DE NUCLEOS DE CELULAS HEPATICAS

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El núcleo de células hepáticas incorpora ácidos grasos saturados y poliinsaturados en los lípidos por un mecanismo acil-CoA dependiente, con especificidad respecto al ácido.
Dra. Ana Ves-Losada Autor:
Ana Ves-Losada
Columnista Experta de SIIC

Institucion:
 Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Facultad de Ciencias Exactas, UN LP, La Plata, Argentina

Artículos publicados por Ana Ves-Losada 
participaron en la investigación
Sabina M. Maté (Licenciada en Biología, Zoóloga)* Rodolfo R. Brenner (Doctor en Química)*
*Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)

Recepción del artículo: 19 de Noviembre, 2002

Aprobación: 4 de Enero, 2003

Primera edición: 28 de Enero, 2003
Segunda edición, ampliada y corregida:  4 de Septiembre, 2003
Resumen
Se estudió la incorporación de ácidos 18:0, 18:2n-6 y 20:4n-6 en núcleos hepáticos incubando in vitro núcleos con el ácido graso [1-14C]. Los [1-14C] acyl-CoAs se esterificaron principalmente a fosfolípidos y a tri acilglicéridos, y en menor proporción a diacilglicéridos. Solo [1-14C]18:2n-6 se esterificó a ésteres de colesterol (EC). El citosol no modificó la incorporación. Se determinó la incorporación de [1-14C]20:4n-6-CoA en los pooles de fosfatidilcolina (FC) nuclear, determinando las especies moleculares marcadas de FC. De las 15 especies moleculares de FC nuclear, se marcaron cinco: 18:0-20:4, 16:0-20:4, 18:1-20:4, 18:2-20, 20:4-20:4. La especie molecular minoritaria, 20:4- 20:4 FC, presentó la mayor radiactividad específica. En conclusión, el núcleo incorpora ácidos grasos saturados y poliinsaturados en los lípidos por un mecanismo acil-CoA dependiente, con especificidad respecto al ácido. El núcleo esterifica 20:4n-6-CoA exógeno en los pooles mayoritarios del ácido, pero con distribución al azar de los ácidos grasos. Primero se sintetizan especies moleculares de FC con ácidos grasos insaturadas en posiciones sn-1 y sn-2. En una segunda etapa, por un proceso de remodelado acil-CoA dependiente, se restablece la distribución asimétrica de ácidos grasos de la FC con un ácido graso satura do esterificado en la posición sn-1 y uno insaturado en la posición sn-2.

Palabras clave
Núcleo, incorporación de ácidos grasos, Acil-CoA, ácido esteárico (18:0), ácido linoleico (18:2n-6), ácido araquidónico (20:4n-6), especies moleculares de FC.

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Artículos originales> Expertos de Iberoamérica>
página www.siicsalud.com/des/des031/03127002.htm

Especialidades
Principal: Medicina General
Relacionadas: Diagnóstico por Laboratorio,  Endocrinología y Metabolismo

Enviar correspondencia a:
Dr. Ana Ves-Losada, INIBIOLP, Facultad de Ciencias Médicas, calles 60 y 120, 1900-La Plata, Argentina.

Patrocinio y reconocimiento
Al CONICET, a la Universidad Nacional de La Plata y a la Agencia Nacional de Promoción Científica y Tecnológica por los subsidios otorgados que financiaron este trabajo. Asimismo los autores quieren agradecer el asesoramiento técnico en HPLC a Ana Bernasconi y a la traductora Norma Beatríz Tedesco en la preparación del manuscrito.
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INCORPORATION AND DISTRIBUTION OF SATURATED AND UNSATURATED FATTY ACIDS INTO NUCLEAR LIPIDS OF HEPATIC CELLS

Abstract
Liver nuclear incorporation of 18:0, 18:2n-6 and 20:4n-6 acids was studied by incubation in vitro of [1-14C] fatty acids with nuclei. [1- 14C] acyl - CoAs were esterified mainly to phospholipids and triacylglycerols; in a minor proportion to diacylglycerols; only [1-14C] 18:2n-6 - CoA to cholesterol esters. The incorporation was not modified by cytosol. Incorporation of [1-14C] 20:4n-6-CoA into nuclear phosphatidyl choline (PC) pools was also studied determining nuclear-labeled PC molecular species. From the 15 PC nuclear molecular species, 5 were labeled with [1- 14C] 20:4n-6-CoA: 18:0-20:4, 16:0-20:4, 18:1-20:4, 18:2-20:4 and 20:4-20:4. The highest specific radioactivity was found in 20:4-20:4 PC. In conclusion, liver nuclei possess the enzymes to incorporate saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver nuclei also utilize exogenous 20:4n-6-CoA to synthesize the major nuclear pools of 20:4n-6, but with a random fatty acid distribution. Firstly, PC molecular species are synthesized with an unsaturated fatty acid at the sn-1 and sn-2 position. Then, the asymmetric distribution of fatty acids of PC with a saturated fatty acid esterified at the sn-1 position and an unsaturated one at sn-2, is reestablished by means of an acyl - CoA - dependent remodeling process.

Key words
Nucleus, incorporation of fatty acids, acil-CoA, stearic acid (18:0), linoleic acid (18:2n-6), arachidonic acid (20:4n-6), phosphatidyl choline molecular species.

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Especialidad principal:
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