绿原酸对凡纳滨对虾抗氧化系统及抗低盐度胁迫的影响

对绿原酸调节凡纳滨对虾(Litopenaeus vannamei)血淋巴抗氧化系统功能及抗低盐度胁迫的效果进行了评价。360尾凡纳滨对虾随机分为4组,分别投喂含有0、100、200和400 mg/kg绿原酸的饲料28 d,随后将对虾从盐度为32的天然海水直接转入至盐度为10的水中胁迫72 h。结果表明,在正常养殖条件下,绿原酸对凡纳滨对虾的成活率、血淋巴总抗氧化能力(Total antioxidative capacity, T-AOC)、超氧化物歧化酶(Superoxide dismutase, SOD)及过氧化氢酶(Catalase, CAT)活力均无明显影响,然而投喂含有绿原酸的饲料14 d,对虾血淋巴谷胱甘肽过氧化物酶(Glutathione peroxidase, GPx)活性和血淋巴细胞GPx和CAT基因表达水平均显著高于对照组(P<0.05);低盐度胁迫24 h,绿原酸组凡纳滨对虾的存活率较对照组提高10%,但各组之间无显著性差异(P>0.05);低盐度胁迫24 h,各组凡纳滨对虾血淋巴T-AOC、SOD和GPx活性与胁迫前相比均显著增加,说明低盐度胁迫条件下机体产生了抗氧化胁迫反应,同时绿原酸组对虾血淋巴GPx、CAT活性均显著高于对照组(P<0.05);低盐度胁迫72 h,绿原酸组对虾血淋巴T-AOC、GPx和CAT活性和血淋巴细胞GPx和CAT基因表达水平均明显高于对照组。上述结果表明绿原酸可有效调节凡纳滨对虾的抗氧化系统功能,增强对虾对于低盐度胁迫下的适应能力。

Effects of dietary chlorogenic acid supplementation on antioxidant system and anti-low salinity of Litopenaeus vannamei

Intensively-reared white shrimp Litopenaeus vannamei are subjected to various environmental stresses that can have severe effects on their physiology. For example, low salinity stress decreases the activity of antioxidant enzymes. How to reduce the adverse effects of multiple environmental stresses on shrimp has become a new challenge in aquaculture. Chlorogenic acid has been documented to effectively scavenge free radicals and improve antioxidant defenses in humans and animals. The objectives of this study were to evaluate the effects of chlorogenic acid on the antioxidant system of L. vannamei, and determine whether it protects the shrimp against low salinity stress. A total of 360 shrimps with an average initial body weight of about 6.7 g were divided randomly into four replicated (×3) treatments, and reared indoors in 500-L glass-fiber tanks containing 300 L of natural seawater. The shrimp were fed one of four diets, a control diet without chlorogenic acid, and three diets containing different levels (100, 200, 400 mg/kg diet) of chlorogenic acid. Shrimps in each treatment were hand-fed one of the four diets to apparent satiation three times daily; uneaten food and feces were removed by siphoning. Prior to the beginning of the feeding trial, all shrimps were acclimatized for one week. Each tank was continuously oxygenated using an air pump, and 30% of the seawater was renewed daily. During the experimental period, water temperature, salinity, pH and other water quality parameters were kept stable. After being fed for 28 days, all shrimps were subjected to acute low salinity stress in which salinity was decreased rapidly from 32 to 10 for 72 h. The results indicated that at normal salinity (32), there were no significant differences in the survival, the total antioxidant status (T-AOC), superoxide dismutase (SOD) and catalase (CAT) activities of the hemolymph of white shrimps that were fed diets with or without chlorogenic acid. However, the glutathione peroxidase (GPx) activity and gene expression of GPx and CAT of shrimp hemolymph increased significantly (P<0.05) when shrimps were, for 14 days, fed diets containing different concentrations of chlorogenic acid. After exposure to low-salinity seawater for 24 h, survival of shrimps fed diets supplemented with chlorogenic acid increased by 10% compared with the control treatment, although the difference between the control and treatments was not significant (P>0.05). Activities of T-AOC, SOD and GPx of shrimp hemolymph in all treatments increased significantly after 24 h of low salinity stress, which suggests that low salinity induced an antioxidant stress response in the shrimps. Moreover, GPx and CAT activities of hemolymph in shrimp fed diets supplemented with chlorogenic acid were significantly higher than those fed the control diet after 24 h of low salinity stress (P<0.05). Over a period of 72 h of exposure to low salinity, activities of T-AOC, GPx and CAT, along with gene expression of GPx and CAT of hemolymph in white shrimp fed dietary chlorogenic acid, were significantly higher than those measured in the control animals. In conclusion, the findings of this study suggest that chlorogenic acid can serve as an effective antioxidant to regulate the antioxidant defense system of white shrimp and improve resistance against low salinity stress.