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First published online June 26, 2009
Journal of Experimental Biology 212, 2254-2260 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.029025
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Targets for TNF{alpha}-induced lipolysis in gilthead sea bream (Sparus aurata L.) adipocytes isolated from lean and fat juvenile fish

Lourdes Cruz-Garcia1, Alfonso Saera-Vila2, Isabel Navarro1, Josep Calduch-Giner2 and Jaume Pérez-Sánchez2,*

1 Departament de Fisiología, Facultat de Biología, Universitat de Barcelona, 08028 Barcelona, Spain
2 Instituto de Acuicultura de Torre de la Sal (CSIC), Departamento de Biología, Cultivo y Patología de Especies Marinas, 12595 Ribera de Cabanes, Castellón, Spain

* Author for correspondence (e-mail: jperez{at}iats.csic.es)

Accepted 20 April 2009

The present study aimed to analyze adiposity heterogeneity and the role of liver X receptor (LXR{alpha}) and peroxisome proliferator-activated receptors (PPARs) as targets of tumour necrosis factor-{alpha} (TNF{alpha}) in gilthead sea bream (Sparus aurata L.). The screening of 20 fish at the beginning of the warm season identified two major groups with fat and lean phenotypes. Fat fish showed increased liver and mesenteric fat depots. This increased adiposity was concurrent in the adipose tissue to enhanced expression of lipoprotein lipase (LPL) whereas mRNA levels of the hormone-sensitive lipase (HSL) remained almost unchanged. The resulting LPL/HSL ratio was thereby highest in fat fish, which suggests that this group of fish has not reached its peak fat storage capacity. This is not surprising given the increased expression of PPAR{gamma} in the absence of a counter-regulatory raise of TNF{alpha}. However, this lipolytic cytokine exerted dual effects in primary adipocyte cultures that differ within and between lean and fat fish. One set of fat fish did not respond to TNF{alpha} treatment whereas a second set exhibited a lipolytic response (increased glycerol release) that was apparently mediated by the downregulated expression of PPARβ. In lean fish, TNF{alpha} exerted a strong and non-transcriptionally mediated lipolytic action. Alternatively, TNF{alpha} would inhibit lipid deposition via the downregulated expression of adipogenic nuclear factors (PPAR{gamma} and LXR{alpha}). TNF{alpha} targets are therefore different in fish with lean and fat phenotypes, which is indicative of the complex network involved in the regulation of fish lipid metabolism.

Key words: lipoprotein lipase, hormone-sensitive lipase, PPAR{alpha}, PPARβ, PPAR{gamma}, LXR{alpha}


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