Data from: Enzyme polymorphism, oxygen and injury: a lipidomic analysis of flight-induced oxidative damage in a SDH-polymorphic insect

When active tissues receive insufficient oxygen to meet metabolic demand, succinate accumulates and has two fundamental effects: it causes ischemia-reperfusion injury while also activating the hypoxia-inducible factor pathway (HIF). The Glanville fritillary butterfly (Melitaea cinxia) possesses a balanced polymorphism in Sdhd, shown previously to affect HIF pathway activation and tracheal morphology and used here to experimentally test the hypothesis that variation in succinate dehydrogenase affects oxidative injury. We stimulated butterflies to fly continuously in a respirometer (3 min duration), which typically caused episodes of exhaustion and recovery, suggesting a potential for cellular injury from hypoxia and reoxygenation in flight muscles. Indeed, flight muscle from butterflies flown on consecutive days had lipidomic profiles similar to rested paraquat-injected butterflies, but distinct from rested untreated butterflies. Many butterflies showed a decline in flight metabolic rate (FMR) on Day 2, and there was a strong inverse relationship between the ratio of Day 2 to Day 1 FMR and the abundance of sodiated adducts of phosphatidylcholines and coenzyme Q (CoQ). This result is consistent with elevation of sodiated lipids caused by disrupted intracellular ion homeostasis in mammalian tissues after hypoxia-reperfusion. Butterflies carrying the Sdhd M allele had higher abundance of lipid markers of cellular damage, but the association was reversed in field-collected butterflies, where focal individuals typically flew for seconds at a time rather than continuously. These results indicate that Glanville fritillary flight muscles can be injured by episodes of high exertion, but injury severity appears to be determined by an interaction between SDH genotype and behavior (prolonged vs. intermittent flight).

当活跃组织供氧不足无法满足代谢需求时，琥珀酸会累积并产生两种核心效应：一方面引发缺血-再灌注损伤，另一方面激活缺氧诱导因子通路（hypoxia-inducible factor pathway, HIF）。格纹蛱蝶（Melitaea cinxia）在Sdhd基因位点存在平衡多态性，既往研究表明该多态性会影响HIF通路激活与气管形态，本研究借此通过实验验证“琥珀酸脱氢酶（succinate dehydrogenase）的变异会影响氧化损伤”这一假说。我们通过呼吸测定仪刺激蝴蝶持续飞行3分钟，该过程通常会引发疲劳与恢复交替的阶段，提示飞行肌存在因缺氧-复氧产生细胞损伤的潜在风险。确实，连续两日接受飞行实验的蝴蝶，其飞行肌的脂质组学特征与经百草枯（paraquat）处理后静置的蝴蝶相似，但与未处理且静置的蝴蝶存在显著差异。许多蝴蝶在第2日的飞行代谢率（flight metabolic rate, FMR）出现下降，且第2日与第1日FMR的比值，与磷脂酰胆碱（phosphatidylcholines）和辅酶Q（coenzyme Q, CoQ）的钠加合物丰度呈显著负相关。该结果与“哺乳动物组织在缺氧-复氧后，细胞内离子稳态紊乱引发钠结合脂质升高”的现象相符。携带Sdhd M等位基因的蝴蝶，其细胞损伤脂质标志物丰度更高，但这一关联在野外采集的蝴蝶中出现反转——野外个体通常仅单次飞行数秒，而非持续飞行。本研究结果表明，格纹蛱蝶的飞行肌可因高强度飞行阶段产生损伤，而损伤严重程度似乎由SDH基因型与飞行行为（持续飞行 vs. 间歇飞行）的相互作用所决定。