青藏高原土著鸟类和移居鸟类的糖脂代谢特征和调节机制比较研究

The Qinghai-Tibet plateau (QTP) is known as "the third pole of the Earth". The animals inhabiting on the QTP have to deal with the selective pressure of “how to enhance their aerobic metabolisms in such hypoxia environment”. Glucose and lipids as the two important energetic substrates, previous studies have shown that there are two distinct hypotheses on the energetic substrate utilization of high-altitude mammals: “Oxygen constraints hypothesis (prefer to utilize glucose)” and “Energy constraints hypothesis (prefer to utilize lipids)”. As volant animals, birds have much higher metabolic rate and energetic demands than mammals, but unfortunately, little is known on the energetic substrate utilization of high-altitude birds in the world. Based on the updated researches and our previous findings, we hypothesized the native birds of the QTP may have obtained the ability to utilize lipids as energetic fuels than the non-native birds. The current project, using both the native species, white-rumped snowfinch, on the QTP, the non-native species, Eurasian tree sparrow, from both the QTP and low-altitude areas, proposes to compare their respiratory quotient (RQ), plasma hormones, the concentration of glucose and lipid metabolites and the activity of related enzymes in organ or tissue, select the key genes, proteins, and metabolites involved in the process of aerobic metabolisms. Our results provide an opportunity to uncover the features and regulatory mechanisms in the process of glucose and lipid metabolism of free-living birds on the QTP, and examine our hypothesis in both the native and non-native bird species from short-term adaptation and long-term evolution aspects, respectively. Moreover, our results would contribute to better understanding the eco-physiological strategies, and the mechanisms of adaption and evolution of high-altitude animals.

青藏高原被称为“地球第三极”，在低氧环境中青藏高原动物如何增加有氧代谢能力是其面临的重要选择压力。糖类和脂类均为有氧代谢的能量底物，高原哺乳动物能量底物利用方式有糖类为主的“氧制约”和脂类为主的“能量制约”两种假说。鸟类因适应飞翔生活而具较高的代谢率和能量需求，但国内外对高原鸟类能量代谢特征的报道匮乏。基于国内外最新进展和前期基础，项目组提出“青藏高原土著鸟类的能量底物以脂类为主，而移居鸟类以糖类为主”的假设。本项目采用整合生物学方法，比较青藏高原土著鸟类、移居鸟类和低海拔区鸟类在糖皮质激素作用下的呼吸熵、血浆激素、器官或组织内糖脂代谢物含量及代谢酶活性的差异；并采用组学技术筛选参与调节能量代谢的关键基因、蛋白和代谢物。研究结果从短期适应和长期进化两个层次检验上述假说，对解析野生鸟类适应青藏高原极端环境的糖脂代谢特征和调节机制，对深入认识高原动物的生理生态适应策略具有重要的理论意义。

青藏高原具有典型的低温和低氧环境特征，青藏高原鸟类如何增加有氧代谢和产热能力以应对冬季寒冷环境是动物适应极端环境领域的热点。鉴于糖类和脂类均为有氧代谢的能量底物，本项目基于国内外最新进展和前期工作基础，提出了“青藏高原土著鸟类的能量底物以脂类为主，而移居鸟类以糖类为主”的假设。本项目比较了青藏高原两种土著鸟类（白腰雪雀和棕颈雪雀）、移居鸟类（树麻雀）和低海拔区鸟类（树麻雀）的呼吸代谢率、呼吸熵、发现高海拔种类均具有低代谢和低呼吸熵的特征，表明青藏高原极端环境选择压力作用下驱动了高海拔鸟类（土著物种和移居物种类似）在代谢表型水平获得了适应极端环境的生理生态策略。在急性应激过程中，这些鸟类在特定器官或组织（肝脏、心肌）内的糖脂代谢物含量和代谢酶活性的变化存在种间差异，发现青藏高原两种土著鸟类—白腰雪雀和棕颈雪雀在能量底物利用方面表现出一系列差异特征，且均不同于青藏高原树麻雀，表明与低海拔近缘种相比，高海拔土著鸟类和移居鸟类仍具有适应极端环境的“特殊的”和“多样的”能量底物利用方式。为阐述高、低海拔环境的同一物种代谢特征及相关通路中的差异，本项目还进一步比较了青藏高原和低海拔区树麻雀能量代谢通路中差异表达的关键蛋白、乙酰化修饰位点和能量代谢物，探讨了高海拔和低海拔同一物种在不同层面（蛋白质、蛋白质乙酰化修饰和代谢效应物）表现出的差异化特征，解析了青藏高原鸟类低代谢特征及能量底物利用方式（偏于脂类为主而非糖类）的分子基础。本项目的研究结果从短期适应和长期进化两个层次探讨了青藏高原鸟类的能量代谢底物利用方式既表现出“特殊性”，又存在“多样性”的特征，这对深入认识高原动物适应极端环境的生理生态策略与机制具有重要的理论价值。