Molecular characterization of a gilthead sea bream (Sparus aurata) muscle tissue cDNA for carnitine palmitoyltransferase 1B (CPT1B)

Understanding the control of piscine fatty acid metabolism is important for determining the nutritional requirements of fish, and hence for the production of optimal aquaculture diets. The regulation and expression of carnitine palmitoyltransferase 1 (CPT1; EC No 2.3.1.21) are critical processes in the control fatty acid metabolism, and here we report a cDNA from gilthead sea bream (Sparus aurata) which encodes a protein with high identity to vertebrate CPT1. This sea bream CPT1 mRNA is predominantly expressed in skeletal and cardiac muscle, with little expression in other tissues. Phylogenetic analysis of other vertebrate CPT1 sequences show that fish genomes contain a single gene related to mammalian CPT1B, and a further two multi-gene families related to mammalian CPT1A. Genes related to mammalian CPT1C are absent in fish. Therefore, based on both functional and evolutionary orthology to mammalian CPT1B, the sea bream CPT1 reported here is a CPT1B isoform. Sea bream CPT1B mRNA expression progressively decreases in heart and muscle up to 12 hours after last feeding, but returns to initial, non-fasted levels after 72 hours. In contrast, in liver non-fasted expression is low, but strongly increases at 24 and 72 hours after last feeding. In white muscle and liver, CPT1B mRNA expression is highly correlated with the expression of peroxisomal proliferator-activated receptor ı (PPARı).Thus fatty acid metabolism by CPT1B and its control by PPARs is similar in fish and mammals, but multiple genes for CPT1A-like proteins in fish also suggest different and more complex pathways of lipid utilisation than in mammals

Molecular characterization of three peroxisome proliferator-activated receptors from the sea bass (Dicentrarchus labrax)

Peroxisome proliferator-activated receptors (PPAR) are nuclear hormone receptors that control the expression of genes involved in lipid homeostasis in mammals. We searched for PPAR in sea bass, a marine fish of particular interest to aquaculture, after hypothesizing that the physiological and molecular processes that regulate lipid metabolism in fish are similar to those in mammals. Here, we report the identification of complementary DNA and corresponding genomic sequences that encode three distinct PPAR from sea bass. The sea bass PPAR are the structural homologs of the mammalian PPARα, β/δ and γ isotypes. As revealed by RNase protection, the tissue expression profile of the fish PPAR appears to be very similar to that of the mammalian PPAR homologs. Thus, PPARα is mainly expressed in the liver, PPARγ in adipose tissue, and PPARβ in all tissues tested, with its highest levels in the liver, where it is also the dominant isotype expressed. Like mammalian PPAR, the sea bass isotypes recognize and bind to PPAR response elements of both mammalian and piscine origin, as heterodimers with the 9-cis retinoic acid receptor. Through the coactivator-dependent receptor ligand assay, we also demonstrated that natural FA and synthetic hypolipidemic compounds can act as ligands of the sea bass PPARα and β isotypes. This suggests that the sea bass PPAR act through similar mechanisms and perform the same critical lipid metabolism functions as mammalian PPAR

Primers and Polymerase Chain Reaction Conditions for DNA Barcoding Teleost Fish based on the Mitochondrial Cytochrome b and Nuclear Rhodopsin Genes.

This report describes a set of 21 polymerase chain reaction primers and amplification conditions developed to barcode practically any teleost fish species according to their mitochondrial cytochrome b and nuclear rhodopsin gene sequences. The method was successfully tested in more than 200 marine fish species comprising the main Actinopteygii family groups. When used in phylogenetic analyses, its combination of two genes with different evolutionary rates serves to identify fish at the species level. We provide a flow diagram indicating our validated polymerase chain reaction amplification conditions for barcoding and species identification applications as well as population structure or haplotyping analyses, adaptable to high-throughput analyses.JRC.G.4-Maritime affair

Conjugated Linoleic Acid Affects Lipid Composition, Metabolism, and Gene Expression in Gilthead Sea Bream (Sparus aurata L)

To maximize growth, farmed fish are fed high-fat diets, yet this can lead to high tissue lipid concentrations with impacts on quality. Given that intake of conjugated linoleic acid (CLA) reduces body fat in mammals, this study determines the effects of dietary CLA on growth, composition and postprandial metabolic variables in sea bream. Fish were fed three diets containing 48 g/100g protein and 24 g/100g fat including fish oil supplemented with 0 (control), 2 or 4% CLA for 12 wk. Feed intake and growth were lower in fish fed the CLA diets compared to controls. Feed efficiency was greater in fish fed the 2% CLA diet and total body fat was lower for the CLA diets versus controls. Circulating growth hormone remained unchanged but somatolactin levels were lower in CLA-fed fish. Tissue fatty acid composition changes were related to lower hepatic fatty acyl desaturase and elongase mRNA levels in fish fed CLA. Liver triglyceride levels were higher in fish fed 4% CLA and muscle levels were lower in fish fed both CLA diets versus controls. Most metabolic differences between controls and CLA-fed fish occurs at 6h but not at 24h after the last meal. These included lower postprandial circulating triglyceride concentrations, greater hepatic acyl-CoA-oxidase and lower L-3-hydroxyacyl-CoA dehydrogenase activities, as markers of peroxisomal and mitochondrial β-oxidation respectively, in CLA-fed fish. Our data suggest that CLA intake channels dietary lipid away from adipose tissue to liver, and a switch from hepatic mitochondrial to peroxisomal β-oxidation, possibly as a detoxification response