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，琥珀酸会发生累积，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）。吉兰维尔蛱蝶（Glanville fritillary butterfly，学名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可影响HIF通路激活与气管形态，本研究借此实验验证“琥珀酸脱氢酶（succinate dehydrogenase, SDH）的变异会影响氧化损伤”这一假说。我们通过呼吸测量仪（respirometer）诱导蛱蝶持续飞行3分钟，该过程通常会引发衰竭与恢复交替的阶段，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，连续两日飞行的蛱蝶，其飞行肌的脂质组学（lipidomic）图谱与经百草枯（paraquat）处理后静置的蛱蝶相似，但与未处理静置的蛱蝶存在显著差异。多数蛱蝶在第二日的飞行代谢率（flight metabolic rate, FMR）出现下降，且第二日与第一日FMR的比值与磷脂酰胆碱（phosphatidylcholines）及辅酶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-复氧后因细胞内离子稳态失衡引发的钠结合脂质升高现象一致。携带Sdhd M等位基因（allele）的蛱蝶，其细胞损伤脂质标志物的丰度更高，但这一关联在野外采集的蛱蝶中恰好相反——野外个体通常单次飞行仅数秒，而非持续飞行。上述结果表明，吉兰维尔蛱蝶的飞行肌可因高强度飞行阶段受到损伤，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）之间的互作所决定。