Goymann Wolfgang, Lupi Sara, Kaiya Hiroyuki, Cardinale Massimiliano, Fusani Leonida
Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, D-82319 Seewiesen, Germany.
Department of Life Sciences and Biotechnology, University of Ferrara, 44100 Ferrara, Italy.
Proc Natl Acad Sci U S A. 2017 Feb 21;114(8):1946-1951. doi: 10.1073/pnas.1619565114. Epub 2017 Feb 6.
Billions of birds migrate long distances to either reach breeding areas or to spend the winter at more benign places. On migration, most passerines frequently stop over to rest and replenish their fuel reserves. To date, we know little regarding how they decide that they are ready to continue their journey. What physiological signals tell a bird's brain that its fuel reserves are sufficient to resume migration? A network of hormones regulates food intake and body mass in vertebrates, including the recently discovered peptide hormone, ghrelin. Here, we show that ghrelin reflects body condition and influences migratory behavior of wild birds. We measured ghrelin levels of wild garden warblers () captured at a stopover site. Further, we manipulated blood concentrations of ghrelin to test its effects on food intake and migratory restlessness. We found that acylated ghrelin concentrations of garden warblers with larger fat scores were higher than those of birds without fat stores. Further, injections of unacylated ghrelin decreased food intake and increased migratory restlessness. These results represent experimental evidence that appetite-regulating hormones control migratory behavior. Our study lays a milestone in migration physiology because it provides the missing link between ecologically dependent factors such as condition and timing of migration. In addition, it offers insights in the regulation of the hormonal system controlling food intake and energy stores in vertebrates, whose disruption causes eating disorders and obesity.
数十亿只鸟类长途迁徙，要么前往繁殖地，要么前往更适宜的地方过冬。在迁徙过程中，大多数雀形目鸟类经常中途停留休息，补充能量储备。到目前为止，我们对它们如何判断自己准备好继续旅程知之甚少。哪些生理信号会告诉鸟类大脑其能量储备足以恢复迁徙？激素网络调节脊椎动物的食物摄入和体重，包括最近发现的肽激素胃饥饿素。在这里，我们表明胃饥饿素反映身体状况并影响野生鸟类的迁徙行为。我们测量了在中途停留地捕获的野生花园莺（）的胃饥饿素水平。此外，我们操纵胃饥饿素的血液浓度，以测试其对食物摄入和迁徙不安的影响。我们发现脂肪评分较高的花园莺的酰化胃饥饿素浓度高于没有脂肪储备的鸟类。此外，注射未酰化的胃饥饿素会减少食物摄入并增加迁徙不安。这些结果代表了食欲调节激素控制迁徙行为的实验证据。我们的研究在迁徙生理学上树立了一个里程碑，因为它提供了诸如迁徙条件和时间等生态相关因素之间缺失的联系。此外，它为控制脊椎动物食物摄入和能量储存的激素系统的调节提供了见解，该系统的紊乱会导致饮食失调和肥胖。
