Protective effects of dietary α-lipoic acid on abalone Haliotis discus hannai against the oxidative damage under waterborne cadmium stress

A 60-day feeding trial was conducted to investigate the protective effects of dietary alpha-lipoic acid (LA) on juvenile abalone Haliotis discus hannai against the oxidative damage under waterborne cadmium (Cd) stress. Three experimental diets were formulated with 0 (Control), 700 (LA-700) and 2100 (LA-2100) mg/kg supplement of LA respectively. Each diet was randomly assigned to three replicates of 50 abalones (initial body weight: 3.17 +/- 0.01 g), which were exposed to 0.35 mg/L of waterborne Cd. Results showed that abalones' Cd bioaccumulation in the serum, mantle, gill, muscle and hepatopancreas were significantly reduced in LA supplement groups. Besides, in hepatopancreas, the activities of antioxidative enzymes and concentration of glutathione (GSH) in LA supplement group were significantly higher than those in control. Meanwhile, in hepatopancreas, LA-2100 group showed a significantly decreased malondialdehyde (MDA) concentration and the protein carbonyls in LA supplement groups were significantly lower than those in control. Diets with LA supplementation significantly upregulated the mRNA expression of HdhMTF-1 (H. discus hannai metal-responsive transcription factor-1) and HdhMT (H. discus hannai metallothionein), and elevated metallothionein (MT) concentrations in hepatopancreas. In conclusion, it was suggested that dietary LA could alleviate Cd-induced oxidative damage through enhancing antioxidative enzyme activities and upregulating the HdhMTF-1-mediated HdhMT transcription and synthesis.