Lipid peroxidative stress and antioxidant defence status during ontogeny of rainbow trout ( Oncorhynchus mykiss).

The objective of the present study was to characterise some important antioxidant enzymes and their relationships with retinoids and lipid peroxidation during rainbow trout (Oncorhynchus mykiss) early development. Eggs were incubated at 7 degrees C until the swim-up stage whereupon fry were fed two semi-purified diets with 0% (CO) and 8% (OX) oxidised lipid respectively for 2 months at 17 degrees C. The activities and gene expression of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were determined as well as the levels of retinoids, F2-isoprostanes and lipid-soluble fluorescent products (LSFP) at various developmental stages. Only SOD had a detectable activity in embryos which increased during development and was linked with an increase of mitochondrial (SOD2) and cytosolic (SOD1) gene expression. SOD1 and SOD2 mRNA were more abundant in fry fed OX than in fry fed CO. CAT activity and gene expression also increased during development and were higher in fry fed OX compared with fry fed CO. Activity of Se-dependent GPX (Se-GPX) increased during development. The gene expression of cytosolic Se-GPX (GPX1) increased from hatching to 2-month-fed fry. Both phospholipid-hydroperoxide GPX and GPX1 genes were more expressed in fry fed OX than in fry fed CO. Retinoids decreased during development and, by 2 months, were lowered in fry fed OX compared with those fed CO. The levels of LSFP were higher in fry fed OX compared with fry fed CO. The present study demonstrates that antioxidant defence systems are active all through the development of rainbow trout and modulated by feeding oxidised lipid.

A detailed identification study on high-temperature degradation products of oleic and linoleic acid methyl esters by GC-MS and GC-FTIR.

GC-MS and GC-FTIR were complementarily applied to identify oxidation compounds formed under frying conditions in methyl oleate and linoleate heated at 180°C. The study was focused on the compounds that originated through hydroperoxide scission that remain attached to the glyceridic backbone in fats and oils and form part of non-volatile molecules. Twenty-one short-chain esterified compounds, consisting of 8 aldehydes, 3 methyl ketones, 4 primary alcohols, 5 alkanes and 1 furan, were identified. In addition, twenty non-esterified volatile compounds, consisting of alcohols, aldehydes and acids, were also identified as major non-esterified components. Furanoid compounds of 18 carbon atoms formed by a different route were also identified in this study. Overall, the composition of the small fraction originated from hydroperoxide scission provides a clear idea of the complexity of the new compounds formed during thermoxidation and frying.

Multiple peroxisome proliferator-activated receptor beta subtypes from Atlantic salmon (Salmo salar).

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily that functions as critical regulators of lipid and energy homeostasis. Although intensively studied in mammals, their basic biological functions are still poorly understood. The objective of this work was to characterize PPARbeta subtypes in a fish, the Atlantic salmon (Salmo salar), in order to address PPAR function and the regulation of lipid homeostasis in lower vertebrates. The screening of an Atlantic salmon genomic library revealed the presence of four genes for PPARbeta subtypes. Based on comparisons of exons and exon-flanking regions, these genes were assigned into two families, ssPPARbeta1 and ssPPARbeta2, each family containing two isotypes: ssPPARbeta1A and beta1B and ssPPARbeta2A and beta2B. Two full-length cDNAs for ssPPARbeta1A and ssPPPARbeta2A were isolated. Transcripts for ssPPARbeta1A and ssPPARbeta2A have distinct tissue expression profiles, with ssPPARbeta1A predominating in liver and ssPPARbeta2A predominating in gill. Expression levels of mRNA of either isotypes were up to tenfold lower in kidney, heart, spleen, muscle, and brain. In cellular transfection assays, ssPPARbeta1A is activated by monounsaturated fatty acids, 2-bromopalmitate, and mammalian PPARbeta-specific ligand GW501516. In contrast, PPARbeta2A was not activated by any of the compounds tested. Furthermore, ssPPARbeta2A repressed both the basal reporter gene activity and the GW501516-induced activity of ssPPARbeta1A. The results indicate unexpected levels of variety and complexity in PPAR subtype and mechanism of action in lower vertebrates.