Albrecht Elke, Norheim Frode, Thiede Bernd, Holen Torgeir, Ohashi Tomoo, Schering Lisa, Lee Sindre, Brenmoehl Julia, Thomas Selina, Drevon Christian A, Erickson Harold P, Maak Steffen
Institute for Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology, D-18196 Dummerstorf, Germany.
Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway.
Sci Rep. 2015 Mar 9;5:8889. doi: 10.1038/srep08889.
The myokine irisin is supposed to be cleaved from a transmembrane precursor, FNDC5 (fibronectin type III domain containing 5), and to mediate beneficial effects of exercise on human metabolism. However, evidence for irisin circulating in blood is largely based on commercial ELISA kits which are based on polyclonal antibodies (pAbs) not previously tested for cross-reacting serum proteins. We have analyzed four commercial pAbs by Western blotting, which revealed prominent cross-reactivity with non-specific proteins in human and animal sera. Using recombinant glycosylated and non-glycosylated irisin as positive controls, we found no immune-reactive bands of the expected size in any biological samples. A FNDC5 signature was identified at ~20 kDa by mass spectrometry in human serum but was not detected by the commercial pAbs tested. Our results call into question all previous data obtained with commercial ELISA kits for irisin, and provide evidence against a physiological role for irisin in humans and other species.
肌动蛋白鸢尾素被认为是从跨膜前体FNDC5（含III型纤连蛋白结构域5）裂解而来，并介导运动对人体新陈代谢的有益作用。然而，血液中循环的鸢尾素的证据很大程度上基于商业ELISA试剂盒，这些试剂盒基于多克隆抗体（pAb），而这些多克隆抗体此前未针对交叉反应血清蛋白进行过测试。我们通过蛋白质印迹法分析了四种商业pAb，结果显示它们与人和动物血清中的非特异性蛋白有显著的交叉反应。使用重组糖基化和非糖基化鸢尾素作为阳性对照，我们在任何生物样品中均未发现预期大小的免疫反应条带。通过质谱法在人血清中鉴定出约20 kDa的FNDC5特征，但所测试的商业pAb未检测到。我们的结果对以前使用商业ELISA试剂盒获得的所有鸢尾素数据提出质疑，并提供证据反对鸢尾素在人类和其他物种中的生理作用。
