Lim J H, Lee J I, Suh Y H, Kim W, Song J H, Jung M H
Division of Metabolic Disease, Department of Biomedical Science, National Institute of Health, 5 Nokbun-dong, Eunpyung-gu, Seoul 122-701, South Korea.
Diabetologia. 2006 Aug;49(8):1924-36. doi: 10.1007/s00125-006-0278-4. Epub 2006 May 31.
AIMS/HYPOTHESIS: Mitochondrial dysfunction is considered a critical component in the development of diabetes. The aim of this study was to elucidate the molecular mechanisms involved in the development of insulin resistance and diabetes through investigation of mitochondrial retrograde signalling.
Mitochondrial function of C2C12 myotube cells was impaired by genetic (ethidium bromide) and metabolic (oligomycin) stress, and changes in target molecules related to insulin signalling were analysed.
Concomitant with reductions in mitochondrial membrane potential (DeltaPsim) and ATP synthesis, production of IRS1 and solute carrier family 2 (facilitated glucose transporter), member 4 (SLC2A4, formerly known as GLUT4) were reduced. Moreover, serine phosphorylation of IRS1 increased, resulting in decreased tyrosine phosphorylation. This indicates that mitochondrial dysfunction decreases insulin-stimulated SLC2A4 translocation and glucose uptake. Mitochondrial stress activated c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) signalling in a Ca(2+)-dependent manner, and removal of free Ca(2+) by BAPTA-AM, as well as inhibition of JNK and p38 MAPK, abrogated mitochondrial stress-induced reductions in IRS1 and SLC2A4 production. Mitochondrial dysfunction after oligomycin treatment significantly increased levels of activating transcription factor 3 (ATF3), which represses Irs1 promoter activity. Removal of the 5' flanking region of Irs1 demonstrated that the promoter region within 191 bases from the transcription site may be involved in the transcriptional repression of Irs1 by mitochondrial stress.
CONCLUSIONS/INTERPRETATION: We show distinct mitochondrial retrograde signalling, where Irs1 is downregulated through ATF3 in a Ca(2+)-, JNK- and p38 MAPK-dependent manner, and IRS1 is inactivated. Therefore, mitochondrial dysfunction causes aberrant insulin signalling and abnormal utilisation of glucose, as observed in many insulin resistance states.
目的/假设：线粒体功能障碍被认为是糖尿病发生发展的关键因素。本研究旨在通过研究线粒体逆行信号传导，阐明胰岛素抵抗和糖尿病发生发展过程中涉及的分子机制。
通过遗传（溴化乙锭）和代谢（寡霉素）应激损害C2C12肌管细胞的线粒体功能，并分析与胰岛素信号传导相关的靶分子变化。
伴随着线粒体膜电位（ΔΨm）和ATP合成的降低，胰岛素受体底物1（IRS1）和溶质载体家族2（促进性葡萄糖转运蛋白）成员4（SLC2A4，原名GLUT4）的生成减少。此外，IRS1的丝氨酸磷酸化增加，导致酪氨酸磷酸化减少。这表明线粒体功能障碍会降低胰岛素刺激的SLC2A4转位和葡萄糖摄取。线粒体应激以Ca²⁺依赖的方式激活c-Jun氨基末端激酶（JNK）和p38丝裂原活化蛋白激酶（p38 MAPK）信号传导，用BAPTA-AM去除游离Ca²⁺以及抑制JNK和p38 MAPK，可消除线粒体应激诱导的IRS1和SLC2A4生成减少。寡霉素处理后的线粒体功能障碍显著增加了激活转录因子3（ATF3）的水平，ATF3可抑制Irs1启动子活性。去除Irs1的5'侧翼区域表明，转录位点191个碱基内的启动子区域可能参与线粒体应激对Irs1的转录抑制。
结论/解读：我们展示了独特的线粒体逆行信号传导，其中Irs1通过ATF3以Ca²⁺、JNK和p38 MAPK依赖的方式被下调，且IRS1失活。因此，线粒体功能障碍会导致胰岛素信号异常和葡萄糖利用异常，这在许多胰岛素抵抗状态中都有观察到。
