Increased activities of hepatic antioxidant defence enzymes in juvenile gilthead sea bream (Sparus aurata L.) fed dietary oxidised oil: attenuation by dietary vitamin E

Abstract

Previously, we had shown that altering the highly unsaturated fatty acid(HUFA)/vitamin E ratios in sea bream (Sparus aurata) livers significantly affected their peroxidation status, with fish fed the 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 sea bream. A high pro-oxidative stress was induced by feeding diets containing around 7% of the dry weight as n-3HUFA. 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 (α-tocopherol 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 of livers 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 contents 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 TBARS levels were significantly lower in fish fed diets supplemented with vitamin E whereas dietary oxidised oil had no major effects on lipid peroxidation products. Catalase and superoxide dismutase activities were both increased in fish fed dietary oxidised oil and reduced by supplementary vitamin E after 30 days feeding.In contrast glutathione peroxidase was less affected by the diets, and the activities of glutathione-S-transferase and glutathione reductase 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 oxidized 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 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.

Interactive Effects of Copper, Fluorene, and Fluoranthene on Enzymatic Biomarkers and Metallothionein Levels in Crucian Carp (Carassius auratus)

“…Moreover, by metabolizing lipid hydroperoxides in response to ROS production, GST plays a critical role in the antioxidant defense system [32]. In this study, the marked increase of GST activity was observed in the fi sh liver exposed to Fl and Fluo alone.…”

Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

“…However, feeding high HUFA diets resulted in signs of increased peroxidative stress in juvenile marine fish, as evidenced by increased levels of tissue lipid peroxidation products, and some moderate effects on liver antioxidant defence enzyme activities were observed (Tocher et al, 2002a). In a very recent study using diets containing very high levels of n-3 HUFA and pre-oxidised oil, the activity of the enzyme defence system was clearly demonstrated to be increased by feeding oxidised oil and reduced by supplementing the diets with vitamin E in sea bream (Mourente et al 2002). In a related comparative study, the liver antioxidant defence enzymes did not respond to dietary oxidised oil or vitamin E in halibut as occurred in sea bream and turbot suggesting that there may be species differences in this defence system perhaps related to temperature or developmental stage (Tocher et al, 2002b).…”

Dietary leucine improves flesh quality and alters mRNA expressions of Nrf2-mediated antioxidant enzymes in the muscle of grass carp ( Ctenopharyngodon idella )

“…Antioxidant enzymes constitute one of the major cellular protective mechanisms against oxidative stress in fish (Mourente et al, 2002). Activities of antioxidant enzymes are related to their mRNA expression in fish tissue .…”