Increased activities of
hepatic antioxidant defence enzymes in juvenile gilthead sea bream (Sparus
aurata L.) fed dietary oxidised oil: attenuation by dietary vitamin E
G.
Mourente, E. Díaz-Salvago, J.G. Bell, D.R. Tocher-2002
Aquaculture, 214(1-4) : 343-361
Abstract:
Previously, we had shown that altering the highly
unsaturated fatty acid (HUFA)/vitamin E ratios in gilthead sea bream livers
significantly affected their peroxidation status, with fish fed a diet rich
in HUFA and low in vitamin E showing significantly higher values of lipid
peroxidation products, without, however, significant effects on liver
antioxidant defence enzyme activities. The aim of the present trial was to
further characterise the biochemical indicators of peroxidative stress in
juvenile gilthead sea bream. A high pro-oxidative stress was induced by
feeding diets containing around 7% of the dry weight as n-3 HUFA. The
potential peroxidative stress was increased by oxidising the oil, increasing
the peroxide value of the oil some 10-fold. These oils were fed without or
with supplemental vitamin E (a-tocopheryl acetate at 200 mg kg-1
dry diet) giving four diets in total. Fish were sampled after 30 and 60 days
of feeding the experimental diets. None of the diets had any serious
deleterious effects on growth and mortality of the fish during the trial.
Similarly, there were few significant effects due to dietary oxidised oil or
supplementary vitamin E on liver lipid and fatty acid profiles and, in
particular, the proportions of HUFA were not decreased by dietary oxidised
oil. The vitamin E content of the liver reflected the vitamin E content of
the diets but was also affected by dietary oxidised oil being reduced by
oxidised oil in fish fed diets without supplemental vitamin E but,
unexpectedly, increased by oxidised oil in fish fed diets supplemented with
vitamin E. Liver thiobarbituric acid reactive substances (TBARS) levels were
significantly lower in fish fed diets supplemented with vitamin E whereas
dietary oxidised oil had no major effect on lipid peroxidation products.
Catalase (CAT) and superoxide dismutase (SOD) activities were both increased
in fish fed dietary oxidised oil and reduced by supplementary vitamin E
after 30 days feeding. In contrast, glutathione peroxidase (GPX) was less
affected by the diets, and the activities of glutathione-S-transferase (GST)
and glutathione reductase (GR) were only reduced by dietary vitamin E after
60 days of feeding. However, all the enzyme activities were significantly
affected by the duration of feeding, but the number of interactions between
the three factors (time, oil and vitamin E) showed that the relationships
were complicated. In conclusion, the present study showed that feeding diets
containing oxidised oil significantly affected the activities of liver
antioxidant defence enzymes and that dietary vitamin E partially abrogated
these effects. Growth and survival of the fish were relatively unaffected
suggesting that the responses in gilthead sea bream offered effective
protection. However, the duration of feeding the diets of high pro-oxidative
stress was observed to have a hitherto unknown effect, possibly the result
of an adaptive process, but which requires further investigation.
Abbreviations:
AA, all-cis-5,8,11,14-eicosatetraenoic acid (arachidonic acid, 20:4n-6);
CAT, catalase; CDNB, chlorodinitrobenzene; DHA, all-cis-4,7,10,13,16,19-docosahexaenoic
acid (22:6n-3); EPA, all-cis-5,8,11,14,17-eicosapentaenoic
acid (20:5n-3); GPX, glutathione peroxidase Se dependent; GR,
glutathione reductase; GSH, reduced glutathione; GSSH, oxidised glutathione;
GST, glutatione-S-transferase; HUFA, highly unsaturated fatty acids (>/=C20
and with >/=3 double bonds); 8-isoprostane, 8-iso-prostaglandin F2a;
MDA, malondialdehyde; PUFA, polyunsaturated fatty acid; SOD, superoxide
dismutase; TAG, triacylglycerol; TBARS, thiobarbituric acid reactive
substances
(Departamento
de Biología, Facultad de Ciencias del Mar y Ambientalés, Universidad de
Polígono del Rio San Pedro, Apartado 40, Centro Andaluz Superior de
Estudios Marinos (CASEM), ES-11510 Puerto Real, Cádiz, Andalucía, Spain,
e-mail: gabriel.mourente@uca.es)