Antioxidant supplementation can reduce the survival costs of amino acid intake in honeybees

Over-consuming amino acids is associated with reduced survival in many species, including honeybees. The mechanisms responsible for this are unclear but one possibility is that excessive intake of amino acids increases oxidative damage. If this is the case, antioxidant supplementation may help reduce the survival costs of high amino acid intake. We tested this hypothesis in African honeybees (Apis mellifera scutellata) using the major antioxidant in green tea, epigallocatechin-3-gallate (EGCG). We first determined the dose-range of EGCG that improved survival of caged honeybees fed sucrose solution. We then provided bees with eight diets that differed in their ratio of essential amino acids (EAA) to carbohydrate (C) (0:1, 1:250, 1:100, 1:75, 1:50, 1:25, 1:10, 1:5 EAA:C) and also in their EGCG dose (0.0 or 0.4 mM). We found that bees fed sucrose only solution survived better than bees fed EAA diets. Despite this, bees preferred a diet that contained intermediate ratios of EAA:C (ca. 1:25), which may represent the high demands for nitrogen of developing nurse bees. EGCG supplementation improved honeybee survival but only at an intermediate dose (0.3–0.5 mM) and in bees fed low EAA diets (1:250, 1:100 EAA:C). That EGCG counteracted the lifespan reducing effects of eating low EAA diets suggests that oxidative damage may be involved in the association between EAAs and lifespan in honeybees. However, that EGCG had no effect on survival in bees fed high EAA diets suggests that there are other physiological costs of over-consuming EAAs in honeybees.

过度摄入氨基酸与多种物种（包括蜜蜂）的生存率降低有关。负责此现象的机制尚不明确，但一种可能性是氨基酸摄入过量会增加氧化损伤。如果情况确实如此，则抗氧化剂的补充可能有助于降低高氨基酸摄入的生存成本。我们使用绿茶中的主要抗氧化剂表没食子儿茶素-3-没食子酸酯（EGCG）在非洲蜜蜂（Apis mellifera scutellata）中测试了这一假设。首先，我们确定了EGCG的剂量范围，该剂量范围能改善饲喂蔗糖溶液的笼养蜜蜂的生存率。接着，我们向蜜蜂提供了八种不同的饮食，这些饮食在必需氨基酸（EAA）与碳水化合物（C）的比例（0:1，1:250，1:100，1:75，1:50，1:25，1:10，1:5 EAA:C）以及EGCG的剂量（0.0或0.4 mM）上有所不同。我们发现，仅饲喂蔗糖溶液的蜜蜂的存活率高于饲喂EAA饮食的蜜蜂。尽管如此，蜜蜂更喜欢含有中等EAA:C比例（约1:25）的饮食，这可能代表了发育中的看护蜂对氮的高需求。EGCG的补充改善了蜜蜂的生存率，但仅在中等剂量（0.3–0.5 mM）以及饲喂低EAA饮食（1:250，1:100 EAA:C）的蜜蜂中有效。EGCG能够抵消食用低EAA饮食的寿命缩短效应，这表明氧化损伤可能参与了蜜蜂中EAAs与寿命之间的关联。然而，EGCG对饲喂高EAA饮食的蜜蜂的生存率没有影响，这表明在蜜蜂中过度摄入EAAs可能存在其他生理成本。