Evaluation of the antioxidant alpha-lipoic acid in Pompano Trachinotus marginatus (Pisces, Carangidae)
The present work evaluated the anti-oxidant effect of lipoic acid (AL) in fish Trachinotus marginatus. The acute effects were determined by administering different concentrations of LA by injection via intraperitoneal (ip) (experiment I) and chronic by feeding (experiment II). Another experiment was also performed using the dose (via food) that presented the best physiological responses, evaluating the changes in the antioxidant capacity of the fish over time (experiment III). Administration via ip showed antagonistic effects depending on the organ studied. In the liver in the brain, doses of 20 mg AL/kg and 40 mg AL/kg, respectively, improved antioxidant capacity. However, in the liver,the higher doses (40 and 60 mg AL/kg) showed a pro-oxidant effect with increased lipid peroxidation and free iron, and reduced detoxification capacity. In experiment II, the fish were fed for 42 days with a diet containing AL. Administration through food altered the body's lipid metabolism. Fish fed the highest doses (890 and 1367 mg AL/kg of feed) showed reduced growth, protein efficiency and food intake. At these doses there was a reduction in the lipid content in the carcass compared to the fish in the control group. The detoxification capacity was greater at the dose of 890 mg AL/kg of feed in the brain. In the muscle there was a reduction in lipid peroxidation in all treatments with AL, an effect that can be correlated with the reduction of the lipid concentration in the carcass.In experiment III, the fish were fed a diet containing 524 mg AL/kg of feed. Glutathione-S-transferase activity and lipid peroxidation at 10, 20 and 30 days in the brain, muscle, liver and gills were analyzed. In muscle, the reduction in lipid peroxidation occurred at 30 days. Considering the results obtained, we can suggest that 5 juveniles of T. marginatus are treated with AL with an ip dose of 20 mg/kg, because in larger doses there was a pro-oxidant effect of AL in the liver. The inclusion of AL in the diet should be fixed between 316 and 524 mg AL/kg of feed, as it presented the best results in terms of chemoprotection, growth and protein and lipid metabolism. Treatment with AL in the diet shows an increase in the detoxification capacity and a reduction in lipid damage after 30 days.Although the use of LA in aquatic animals is restricted to experimental studies, the results obtained demonstrate that the use of this compound has potential use in aquaculture.