Flight training and dietary antioxidants have mixed effects on the oxidative status of multiple tissues in a female migratory songbird

Birds, like other vertebrates, rely on a robust antioxidant system to protect themselves against oxidative imbalance caused by energy-intensive activities such as flying. Such oxidative challenges may be especially acute for females during spring migration, since they must pay the oxidative costs of flight while preparing for reproduction; however, little previous work has examined how the antioxidant system of female spring migrants responds to dietary antioxidants and the oxidative challenges of regular flying. We fed two diets to female European starlings, one supplemented with a dietary antioxidant and one without, and then flew them daily in a windtunnel for two weeks during the fall and spring migration periods. We measured the activity of enzymatic antioxidants (GPx, SOD, CAT), non-enzymatic antioxidant capacity (ORAC), and markers of oxidative damage (protein carbonyls and lipid hydroperoxides) in four tissues: pectoralis, leg, liver, and heart. Dietary antioxidants affected enzymatic antioxidant activity and lipid damage in the heart, and non-enzymatic antioxidant capacity in the pectoralis and protein damage in leg muscle. In general, birds fed less antioxidants appear to incur increased oxidative damage while upregulating non-enzymatic and enzymatic antioxidant activity, though these effects were strongly tissue-specific. We also found a significant diet x training interaction for enzymatic antioxidant activity in the leg, and strong trends for diet x training interactions for enzymatic antioxidant activity in the heart and liver. Flight-training may condition the antioxidant system of females to dynamically respond to oxidative challenges, and females during spring migration may shift antioxidant allocation to reduce oxidative damage.

鸟类与其他脊椎动物类似，依靠一套强健的抗氧化系统，抵御飞行等高能量消耗活动所引发的氧化失衡。对于春季迁徙的雌性个体而言，此类氧化应激往往更为严峻：它们既要承受飞行带来的氧化代价，同时还要为繁殖活动做好准备；然而此前鲜有研究探讨春季迁徙雌性鸟类的抗氧化系统如何响应膳食抗氧化剂与常规飞行带来的氧化挑战。
本研究为雌性欧洲椋鸟设置两组膳食方案：一组补充膳食抗氧化剂，另一组不做补充；随后在秋季与春季迁徙时段，让它们每日在风洞（wind tunnel）中接受飞行训练，持续两周。我们对四种组织——胸肌、腿部肌肉、肝脏与心脏——中的酶促抗氧化剂（GPx、SOD、CAT）活性、非酶促抗氧化能力（ORAC），以及氧化损伤标志物（蛋白质羰基与脂质氢过氧化物）水平进行了检测。
研究结果显示，膳食抗氧化剂可影响心脏内的酶促抗氧化活性与脂质损伤水平，同时也会改变胸肌的非酶促抗氧化能力以及腿部肌肉的蛋白质损伤水平。总体而言，摄入抗氧化剂较少的鸟类，其氧化损伤程度往往更高，同时会上调非酶促与酶促抗氧化活性，不过这类效应具有显著的组织特异性。我们还发现，腿部的酶促抗氧化活性存在显著的日粮×训练交互效应，而心脏与肝脏的酶促抗氧化活性则表现出强烈的日粮×训练交互趋势。飞行训练或可使雌性个体的抗氧化系统具备动态响应氧化应激的能力，而春季迁徙期的雌性或许会调整抗氧化物质的分配，以降低氧化损伤。