Liu Wei, Tian Xiaojun, Wu Ti, Liu Le, Guo Yanghongyun, Wang Changhua
Department of Otorhinolaryngology, Head and Neck Surgery, The Second People's Hospital of Jingzhou City, Jingzhou, 434000 Hubei, China.
Department of Critical Care Medicine, The Second People's Hospital of Jingzhou City, Jingzhou, 434000 Hubei, China.
Int J Endocrinol. 2019 Jan 15;2019:3054820. doi: 10.1155/2019/3054820. eCollection 2019.
The involvement of phosphodiesterase type 5 (PDE5) in the development of insulin resistance has been reported recently. However, the underlying molecular mechanism remains unclear. The present study aims at investigating the potential impacts of PDE5A on insulin signaling in C2C12 skeletal muscle myotubes and uncover the related mechanism.
C2C12 myoblasts were differentiated into myotubes. Western blot was performed to detect the levels of proteins and phosphorylated proteins. Glucose uptake was determined by a colorimetric kit. The overexpression or knockdown of specific protein was carried out by infecting the myotubes with adenoviruses carrying cDNA or shRNA corresponding to the targeted protein, respectively.
PDE5A was demonstrated to negatively regulate insulin signaling, evidenced by the opposite effects on the suppression or enhancement of the insulin-stimulated Akt phosphorylation and 2-deoxy-D-glucose (2-DG) uptake in C2C12 myotubes, when PDE5A was overexpressed or knockdown, respectively. Interestingly, PDE5A overexpression led to significantly enhanced, while its knockdown resulted in markedly reduced, endoplasmic reticulum (ER) stress. Inhibition of ER stress improved PDE5A overexpression-induced insulin resistance. In addition, PDE5A was found to suppress proteasome activity. Inhibition of PDE5 by its selective inhibitor icariin restored PDE5A overexpression-reduced proteasome activity and mitigated PDE5A overexpression-induced ER stress. Consistently, icariin administration also markedly attenuated the detrimental impacts of PDE5A overexpression on insulin signaling.
These results suggest that PDE5A suppresses proteasome activity, which results in ER stress and subsequent insulin resistance in C2C12 myotubes.
最近有报道称5型磷酸二酯酶（PDE5）参与胰岛素抵抗的发生发展。然而，其潜在的分子机制仍不清楚。本研究旨在探讨PDE5A对C2C12骨骼肌肌管胰岛素信号传导的潜在影响，并揭示相关机制。
将C2C12成肌细胞分化为肌管。采用蛋白质免疫印迹法检测蛋白质和磷酸化蛋白质水平。用比色试剂盒测定葡萄糖摄取。通过分别用携带与靶蛋白对应的cDNA或shRNA的腺病毒感染肌管来实现特定蛋白的过表达或敲低。
PDE5A被证明对胰岛素信号传导起负调节作用，当PDE5A分别过表达或敲低时，对C2C12肌管中胰岛素刺激的Akt磷酸化和2-脱氧-D-葡萄糖（2-DG）摄取的抑制或增强作用呈现相反效果，这证明了该结论。有趣的是，PDE5A过表达导致内质网（ER）应激显著增强，而其敲低则导致内质网应激明显降低。抑制内质网应激可改善PDE5A过表达诱导的胰岛素抵抗。此外，发现PDE5A可抑制蛋白酶体活性。其选择性抑制剂淫羊藿苷抑制PDE5可恢复PDE5A过表达降低的蛋白酶体活性，并减轻PDE5A过表达诱导的内质网应激。一致地给药淫羊藿苷也显著减弱了PDE5A过表达对胰岛素信号传导的有害影响。
这些结果表明，PDE5A抑制蛋白酶体活性，导致内质网应激及随后C2C12肌管中的胰岛素抵抗。
