Icariin induces irisin/FNDC5 expression in C2C12 cells via the AMPK pathway

Backgroud Icariin, a major bioactive pharmaceutical component of the Chinese herbal medicine Epimedii Herba, has demonstrated lipid-lowering and anti-obesity effects. Irisin/ fibronectin type III domain-containing 5 (FNDC5) protects against obesity by inducing browning in white adipose tissue. Objectives This study investigated the effects of icariin on irisin/FNDC5 expression in C2C12 myotubes. Method Cultured murine C2C12 myocytes were used to study the effects of icariin on irisin/FNDC5 expressions by Western-blot, qPCR, Elisa and Immunofluorescence. We also investigated FNDC5 expression in icariin-treated intact mice. Results Icariin increased irisin/FNDC5 protein levels. mRNA levels of irisin/FNDC5 were also increased in C2C12 myocytes after treatment with icariin. Icariin increased peroxisome proliferator-activated receptor gamma co-activator lalpha (PGC-1 alpha) protein and mRNA levels. Additionally, icariin exposure resulted in phosphorylation of AMP-activated protein kinase (AMPK) in a dose-dependent manner. The regulatory effect of icariin on FNDC5 protein expression was blocked by the AMPK antagonist compound C or silencing of AMPK, suggesting that icariin increased FNDC5 protein expression via the AMPK pathway. In vivo, icariin decreased body weight gain in C57BL/ 6 mice and increased FNDC5, PGC-1 alpha, and p-AMPK expression levels in skeletal muscle. Conclusions Taken together, our results indicated that icariin induces irisin/FNDC5 expression via the AMPK pathway, indicating that icariin may be promising as an anti-obesity drug.

背景 淫羊藿苷是中药淫羊藿的一种主要生物活性药用成分，已显示出降脂和抗肥胖作用。鸢尾素/含Ⅲ型纤连蛋白结构域5（FNDC5）通过诱导白色脂肪组织的褐变来预防肥胖。 目的 本研究探讨淫羊藿苷对C2C12肌管中鸢尾素/FNDC5表达的影响。 方法 采用培养的小鼠C2C12肌细胞，通过蛋白质印迹法、定量聚合酶链反应、酶联免疫吸附测定和免疫荧光法研究淫羊藿苷对鸢尾素/FNDC5表达的影响。我们还研究了淫羊藿苷处理的完整小鼠中FNDC5的表达。 结果 淫羊藿苷提高了鸢尾素/FNDC5蛋白水平。用淫羊藿苷处理后，C2C12肌细胞中鸢尾素/FNDC5的信使核糖核酸水平也升高。淫羊藿苷提高了过氧化物酶体增殖物激活受体γ共激活因子1α（PGC - 1α）的蛋白和信使核糖核酸水平。此外，淫羊藿苷暴露以剂量依赖的方式导致腺苷酸活化蛋白激酶（AMPK）磷酸化。AMPK拮抗剂化合物C或AMPK沉默阻断了淫羊藿苷对FNDC5蛋白表达的调节作用，表明淫羊藿苷通过AMPK途径提高FNDC5蛋白表达。在体内，淫羊藿苷降低了C57BL/6小鼠的体重增加，并提高了骨骼肌中FNDC5、PGC - 1α和磷酸化AMPK的表达水平。 结论 综上所述，我们的结果表明淫羊藿苷通过AMPK途径诱导鸢尾素/FNDC5表达，这表明淫羊藿苷作为一种抗肥胖药物可能具有前景。