Effects Of Reduced Glutathione, α-lipoic Acid And The Interaction Between Selenium And Glutathione, Selenium And α-lipoic Acid On Growth And Antioxidation In Japanese Flounder (paralichthys Olivaceus)

A series of experiments were conducted to determine the effects of dietary reduced glutathione (GSH), a-lipoic acid (LA) and the interaction between selenium (Se) and GSH, Se and LA on growth and antioxidation in Japanese Flounder (Paralichthys olivaceus), a marine carnivorous fish. The results of the present study were summarized as follows:Experiment 1:A one-factorial experiment was conducted to determine the effects of gradients of diatary LA on growth and antioxidation in juvenile Japanese flounder (initial weight was 9.39±0.17 g). The juveniles were divided into six triplicate groups, and fed one of the six purified diets (containing 0,200,400,800,1600 or 3200 LA mg/Kg dry diet respectively) for 8 weeks in a flow-through system. A series of indexes were conducted, such as weight gain rate (WGR), survival rate, the concentration of hepatic GSH and malonaldehyde (MDA), the hepatic total antioxidant capacity (T-AOC) and the activities of hepatic glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR) and superoxide dismutase (SOD).The results showed that there were no significant difference in the survival of Japanese Flounder among six dietary treatments(P>0.05). The average WGR reached the significantly highest value in the groups fed the diets with 400 or 800 mg LA, which were significantly higher than those of the other groups (P<0.05). No significant difference was found between groups in the concentrations of hepatic GSH and activities of SOD (P>0.05). The activities of hepatic GST and GR decreased then increased with the increasing of supplied dietary LA (P<0.05). The lowest values of GST were found in the treatments with 400 or 800 mg LA/Kg diet (P<0.05), and the GR value of the treatment with 800 mg LA/Kg diet was significantly higher than the values in other treatments, except for the treatment with 1600 mg LA/Kg diet (P<0.05). The concentrations of hepatic MDA were significantly decreased with rising content of dietary LA (P<0.05), and the concentrations of hepatic MDA with 1600 and 3200 mg LA/Kg diet were significantly lower than the control group with 0 mg/Kg dietary LA (P<0.05). The activities of hepatic GPx and T-AOC increased then decreased with the increasing of supplied dietary LA (P<0.05). The values of GPx in the three treatments with 200,400 and 800 mg LA/Kg diet were significantly higher than the two treatments with 0 arid 3200 mg/Kg dietary LA (P<0.05). The highest value of T-AOC was found in the treatment with 800 mg LA/Kg diet, which was significantly higher than the two treatments with 0 and 3200 mg LA/Kg diet (P<0.05). According to the average WGR data, a broken-line model was employed to calculate the optimal levels of dietary LA, which was 745.05 mg/Kg diet. Deficient or overdose of dietary LA could cause negative effects on the growth and antioxidative capacity of Paralichthys olivaceus.Experiment 2:A one-factorial experiment was conducted to determine the effects of gradients of diatary GSH on growth and antioxidation in juvenile Japanese flounder (initial weight was 9.49±0.22 g). The juveniles were divided into six triplicate groups, and fed on one of the six purified diets (containing 0,97.96,189.92,371.84,688.72 or 1063.56 GSH mg/Kg dry diet respectively) for 8 weeks in a flow-through system. A series of indexes were conducted, such as WGR, survival rate, the concentration of hepatic GSH and MDA, the hepatic T-AOC and the activities of hepatic GPx, GST, GR and SOD.The results showed that survival was not significantly affected by dietary GSH levels (P>0.05). The average WGR in the treatment with 371.84 mg/Kg dietary GSH was significantly higher than those in other treatments (P<0.05). The hepatic GSH concentration in dietary GSH added groups was significantly higher than that in dietary GSH deprived group (control group) (P<0.05). No significant differences in hepatic MDA concentration were found between GSH deprived and supplemented groups (P>0.05). The lowest value of hepatic GR activities was found in treatment with 371.84 mg/Kg dietary GSH (P<0.05). There were no significant differences in the activities of hepatic SOD and GPx among the treatments (P>0.05). In the group with 371.84 mg/Kg dietary GSH, the T-AOC was significantly higher than that in the group with 1063.56 mg/Kg dietary GSH, however, the GST activity was significantly lower than those in the other groups (P<0.05). Based on the WGR data in the present experiment, a broken-line model was employed to calculate the optimal levels of dietary GSH, which was 368.92 mg/Kg diet. Deficient or overdose of dietary GSH could cause negative effects on the growth and anti-oxidative capacity of Paralichthys olivaceus.Experiment 3:A two-factorial experiment was conducted to determine the Se and LA interaction on growth and antioxidation in juvenile Japanese flounder (initial weight was 9.42±0.16 g). Totally nine purified diets were made to provide graded levels of Se (0,1.07,40 mg/Kg, supplied as Na2Se03) and LA (0,800,3200 mg/Kg). The juveniles were divided into nine triplicate groups, and fed on one of the nine purified diets respectively, for 8 weeks in a flow-through system. A series of indexes were conducted, such as WGR, survival rate, the concentration of hepatic GSH and MDA, the hepatic T-AOC and the activities of hepatic GPx, GST, GR and SOD.The results showed that the value of survival in the treatment with both 3200 mg LA/Kg diet and 40 mg Se/Kg diet was significantly lower than other treatments (P<0.05), and there was no significant difference between other groups (all higher than 96.43) (P>0.05). WGR was significantly affected by the interaction between LA and Se (P<0.05). When the diets were provided 0 or 1.07 mg Se/Kg diet, WGR presented a trend to rise in the treatment with 800 mg LA/Kg diet, and WGR reached the highest value in the treatment with both 800 mg LA and 1.07 mg Se/Kg diet, which was significant higher than other groups (P<0.05). Oppositely, in the diets with high selenium level (40 mg/Kg), values of WGR in the LA provided treatments was significantly lower than the control group (0 mg/Kg LA). Hepatic GSH concentration was significantly affected by the interaction between dietary LA and selenium (P<0.05). When dietary Se was deprived or provided 1.07 mg/Kg, the values of hepatic GSH concentration in the treatments provided LA were significantly lower than LA deprived treatments (P<0.05). Nevertheless, between the treatments of high Se level (40 mg/Kg), hepatic GSH concentration of the treatments with LA provided (800 or 3200 mg/Kg) had a rising trend compared with control group (P>0.05). Hepatic MDA concentration was significantly affected by the interaction between dietary LA and Se (P<0.05). The value of hepatic MDA concentration in the treatment with 3200 mg LA/Kg diet was significantly higher than the other two treatments when dietary Se was deprived (P<0.05). The values of hepatic MDA concentration in the treatments provided LA (800 or 3200 mg/Kg) were significantly lower than the control group (0 mg LA/Kg diet) when dietary Se was 1.07 mg/Kg (P<0.05). In the treatments of high Se level (40 mg/Kg), the values of hepatic MDA concentration of the treatment with 3200 mg LA/Kg diet was significantly higher than the other two treatments (P<0.05). The activities of hepatic GPx and GST were significantly affected by the interaction between dietary LA and Se (P<0.05). The highest value of hepatic GPx activity was found in the treatment with both 800 mg LA and 1.07 mg Se/Kg diet, and this value was significantly higher than those in other treatments (P<0.05). The values of hepatic GPx and GST of the treatments with 800 mg LA/Kg diet was significantly higher than those of the treatments with 0 or 3200 mg LA/Kg diet when dietary Se level was invariable (P<0.05). Likewise, the values of hepatic GPx of the treatments with 1.07 mg Se/Kg diet was significantly higher than those of the treatments with 0 or 40 mg Se/Kg diet when dietary LA level was invariable (P<0.05). The lowest values of hepatic GST activity was found in the treatments with 3200 mg LA/Kg diet (P<0.05). The values of hepatic GST of the treatments with 1.07 or 40 mg Se/Kg diet were significantly higher than the control group (0 mg Se/Kg diet) when dietary LA level was invariable (P<0.05). Both T-AOC and the activities of hepatic GR were significantly affected by both dietary LA and Se (P<0.05). The highest values were found in the treatment with both 800 mg LA and 1.07 mg Se/Kg diet, and the two values were significantly higher than those of other treatments, separately (P<.05). No significant difference was found between the diets with grads of LA (P<0.05). SOD activities in the treatments with 40 mg Se/Kg diet were significantly higher than SOD in both the control groups (dietary selenium 0 mg/Kg) and dietary Se 1.07 mg/Kg groups when dietary LA level was invariable (P<0.05).Experiment 4:A two-factorial experiment was conducted to determine Se and GSH interaction on growth and antioxidation in juvenile Japanese flounder (initial weight was 9.49±0.17 g). Totally nine purified diets were made to provide graded levels of Se (0,1.07,40mg/Kg, supplied as Na2Se03) and GSH (0,371.84,1063.56 mg/Kg). The juveniles were divided into nine triplicate groups, and fed on one of the nine purified diets respectively, for 8 weeks in a flow-through system. A series of indexes were conducted, such as WGR, survival rate, the concentration of hepatic GSH and MDA, the hepatic T-AOC and the activities of hepatic GPx, GST, GR and SOD.The results showed that survival was not significantly affected by the interaction between Se and GSH (P>0.05). The values of WGR in the Se provided treatments (1.07 or 40 mg/Kg) were significantly higher than the Se deprived treatments (0 mg/Kg) (P<0.05). The hepatic GSH concentrations were significantly affected by the interaction between GSH and Se (P<0.05). The hepatic GSH concentrations of the treatments with 371.84 mg GSH/Kg diet were significantly higher than those in other treatments when dietary Se level was invariable (P<0.05). Likewise, the hepatic GSH concentrations of the treatments with 1.07 mg Se/Kg diet were significantly higher than those in other treatments when dietary GSH level was invariable (P<0.05). There was no significant difference in hepatic MDA concentrations among nine dietary treatments, and so was the SOD activities (P>0.05). Hepatic GPx activities were significantly affected by dietary GSH levels (P<0.05), moreover hepatic T-AOC and GST, GR activities were significantly affected by the interaction between dietary Se and GSH (P<.05). Both hepatic T-AOC and GST activity in the treatment with 371.84 mg GSH/Kg diet were significantly higher than those in the treatments dealed with 0 or 1063.56 mg GSH/Kg diet when dietary Se was deprived (P<0.05). When dietary Se was 1.07 mg/Kg, the hepatic GST and GR in the treatment with 371.84 mg/Kg was significantly lower compared with the other two treatments with 0 or 1063.56 mg GSH/Kg diet, but T-AOC in 371.84 mg GSH/Kg diet treatment was significantly higher than the other two treatments (P<0.05). When dietary Se was 40 mg/Kg, hepatic GST activity decreased with dietary GSH level increased, and GR activity in dietary GSH 371.84 mg/Kg group was significantly higher than the other two groups (P<0.05).