Brenmoehl Julia, Albrecht Elke, Komolka Katrin, Schering Lisa, Langhammer Martina, Hoeflich Andreas, Maak Steffen
1. Institute for Genome Biology, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany;
2. Institute for Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany;
Int J Biol Sci. 2014 Mar 11;10(3):338-49. doi: 10.7150/ijbs.7972. eCollection 2014.
Recent findings regarding the response of fibronectin type III domain-containing protein 5 (Fndc5) and irisin to exercise are partly controversial. While the 25 kDa form of Fndc5 can be observed in muscle and serum of different species, the ~12 kDa irisin band was not detectable up to now. The present study aimed to clarify whether irisin exists in its theoretical size of ~12 kDa in mice and if it is affected by exercise. Male mice were randomly assigned to a sedentary control group (CO), a group with free access to running wheels (RW), and a treadmill group (TM). Blood and leg muscles were collected to investigate the regulatory cascade including peroxisome proliferator-activated receptor gamma co-activator 1-alpha (Ppargc1a) and Fndc5. In western blot analysis, antibodies were used capable of differentiation between full-length Fndc5 and irisin. This enabled us to demonstrate that irisin exists in muscle and serum of mice independent of exercise and that it is increased immediately after acute exercise. Different transcripts of Ppargc1a mRNA, but not Fndc5 mRNA, were up-regulated in the TM group. Furthermore, neither Fndc5 (25 kDa) nor Ppargc1a protein was elevated in muscle tissue. The Ppargc1a-Fndc5/irisin pathway did not clearly respond to mild exercise in the RW group. Our results provide evidence for the existence of irisin and for its immediate response to acute exercise in mice.
近期关于含III型纤连蛋白结构域蛋白5（Fndc5）和鸢尾素对运动反应的研究结果存在一定争议。虽然在不同物种的肌肉和血清中可观察到25 kDa形式的Fndc5，但截至目前尚未检测到约12 kDa的鸢尾素条带。本研究旨在阐明鸢尾素在小鼠体内是否以其理论大小约12 kDa存在，以及它是否受运动影响。雄性小鼠被随机分为久坐对照组（CO）、可自由使用跑轮的组（RW）和跑步机运动组（TM）。采集血液和腿部肌肉以研究包括过氧化物酶体增殖物激活受体γ共激活因子1α（Ppargc1a）和Fndc5在内的调节级联反应。在蛋白质印迹分析中，使用能够区分全长Fndc5和鸢尾素的抗体。这使我们能够证明鸢尾素独立于运动存在于小鼠的肌肉和血清中，并在急性运动后立即增加。在TM组中，Ppargc1a mRNA的不同转录本上调，但Fndc5 mRNA未上调。此外，肌肉组织中的Fndc5（25 kDa）和Ppargc1a蛋白均未升高。在RW组中，Ppargc1a - Fndc5/鸢尾素途径对轻度运动没有明显反应。我们的结果为鸢尾素的存在及其在小鼠中对急性运动的即时反应提供了证据。
