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This Article Full Text Full Text (PDF) All Versions of this Article: 297/5/R1421    most recent 00312.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Skiba-Cassy, S. Articles by Médale, F. PubMed PubMed Citation Articles by Skiba-Cassy, S. Articles by Médale, F.

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Rainbow trout genetically selected for greater muscle fat content display increased activation of liver TOR signaling and lipogenic gene expression

Unité Mixte de Recherches 1067 Nutrition Aquaculture and Génomique, Institut National de la Recherche Agronomique, Pôle d'hydrobiologie, 64310 Saint Pée-sur-Nivelle, France

Submitted June 8, 2009 ; accepted in final form August 19, 2009

Genetic selection is commonly used in farm animals to manage body fat content. In rainbow trout, divergent selection for low or high muscle fat content leads to differences in utilization of dietary energy sources between the fat muscle line (FL) and the lean muscle line (LL). To establish whether genetic selection on muscle fat content affects the hepatic insulin/nutrient signaling pathway, we analyzed this pathway and the expression of several metabolism-related target genes in the livers of the two divergent lines under fasting and then refeeding conditions. Whereas glycemia returned to basal level 24 h after refeeding in FL trout, it remained elevated in the LL trout. Target of rapamycin (TOR) protein was more abundant in the livers of FL trout than in LL trout, and refeeding activation of the hepatic TOR signaling pathway (TOR, S6K1, and S6) was therefore enhanced. Genes related to glycolysis (glucokinase and pyruvate kinase) and gluconeogenesis (glucose-6-phosphatase and phosphoenolpyruvate carboxykinase) were only slightly affected by refeeding and genetic selection. Refeeding stimulated expression of lipogenic genes and the sterol-responsive element binding protein (SREBP1), and expression of fatty acid synthase, glucose-6-phosphate dehydrogenase, and serine dehydratase was predominant in the livers of FL fish compared with LL fish. In agreement with recent findings linking TOR to lipogenesis control, we concluded that genetic selection for muscle fat content resulted in overactivation of the TOR signaling pathway-associated lipogenesis and probably also improved utilization of glucose.

metabolism; fattening; insulin-target of rapamycin signaling; messenger RNA levels