Service of Internal Medicine, Centre Hospitalier Universitaire Vaudoisand University of Lausanne, Lausanne, Switzerland.
Diabetes. 2011 Dec;60(12):3169-74. doi: 10.2337/db10-1743. Epub 2011 Oct 12.
Increase in adipose cAMP-responsive element binding protein (CREB) activity promotes adipocyte dysfunction and systemic insulin resistance in obese mice. This is achieved by increasing the expression of activating transcription factor 3 (ATF3). In this study, we investigated whether impaired expression of the inducible cAMP early repressor (ICER), a transcriptional antagonist of CREB, is responsible for the increased CREB activity in adipocytes of obese mice and humans.
Total RNA and nuclear proteins were prepared from visceral adipose tissue (VAT) of human nonobese or obese subjects and white adipose tissue (WAT) of C57Bl6-Rj mice that were fed with normal or high-fat diet for 16 weeks. The expression of genes was monitored by real-time PCR, Western blotting, and electromobility shift assays. RNA interference was used to silence the expression of Icer.
The expression of Icer/ICER was reduced in VAT and WAT of obese humans and mice, respectively. Diminution of Icer/ICER was restricted to adipocytes and was accompanied by a rise of Atf3/ATF3 and diminution of Adipoq/ADIPOQ and Glut4/GLUT4. Silencing the expression of Icer in 3T3-L1 adipocytes mimicked the results observed in human and mice cells and hampered glucose uptake, thus confirming the requirement of Icer for appropriate adipocyte function.
Impaired expression of ICER contributes to elevation in CREB target genes and, therefore, to the development of insulin resistance in obesity.
脂肪细胞 cAMP 反应元件结合蛋白（CREB）活性的增加会促进肥胖小鼠脂肪细胞功能障碍和全身胰岛素抵抗，这是通过增加激活转录因子 3（ATF3）的表达来实现的。在这项研究中，我们研究了诱导型 cAMP 早期阻遏物（ICER）的表达受损是否是肥胖小鼠和人类脂肪细胞中 CREB 活性增加的原因，ICER 是 CREB 的转录拮抗剂。
从非肥胖或肥胖受试者的内脏脂肪组织（VAT）和 C57Bl6-Rj 小鼠的白色脂肪组织（WAT）中提取总 RNA 和核蛋白，这些小鼠分别用正常或高脂肪饮食喂养 16 周。通过实时 PCR、Western blot 和电泳迁移率变动分析监测基因的表达。使用 RNA 干扰沉默 Icer 的表达。
肥胖人群的 VAT 和肥胖小鼠的 WAT 中 Icer/ICER 的表达减少。Icer/ICER 的减少仅限于脂肪细胞，并伴有 Atf3/ATF3 的增加和 Adipoq/ADIPOQ 和 Glut4/GLUT4 的减少。在 3T3-L1 脂肪细胞中沉默 Icer 的表达模拟了在人类和小鼠细胞中观察到的结果，并阻碍了葡萄糖摄取，从而证实了 Icer 对适当的脂肪细胞功能的要求。
ICER 表达受损导致 CREB 靶基因升高，从而导致肥胖症中胰岛素抵抗的发展。
