Yi Huahua, Gu Chenjuan, Li Min, Zhang Zhiguo, Li Qingyun, Feng Jing, Zhou Jun, Du Juan
Department of Respiratory Medicine, Ruijin Hospital, No. 197, Ruijin Er Road., Shanghai, 200025, China.
Department of Respiratory Medicine, Ruijin Hospital, No. 197, Ruijin Er Road., Shanghai, 200025, China.
Life Sci. 2017 Jul 15;181:17-22. doi: 10.1016/j.lfs.2017.04.022. Epub 2017 Apr 29.
Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with abnormal glucose metabolism. Nowadays, endoplasmic reticulum (ER) stress emerges as an important mechanism underlying the development of type 2 diabetes mellitus (T2DM). However, it remains unclear that intermittent hypoxia (IH) could induce ER stress, resulting in abnormality of glucose metabolism. Thus, in the current study we explore the changes of insulin signaling under IH and the role of ER stress underlying these changes.
HepG2 cells were exposed to room air (RA) or IH for 8h, 16h and 24h respectively. Oxygen concentration in IH groups was in a dynamic cycle from 21% to 1% every 5min, while it remained at 21% in RA groups. Insulin was added into cell culture medium for AKT and p-AKT measurement. In another experiment set, HepG2 cells were pre-cultured with 4-PBA prior to IH or RA exposure. Expression of AKT, p-AKT, p-JNK, p-IRE1, p-PERK and p-eIF2α was examined by Western Blot.
Compared with RA, p-AKT expression in HepG2 cells under IH for 24h was significantly lower even with insulin treatment. Expression of p-JNK, p-IRE1, ATF6, p-PERK and p-eIF2α were upregulated. p-AKT level in HepG2 with 4-PBA preculture under IH was restored. p-PERK and p-eIF2α expression in HepG2 cells in IH groups with 4-PBA preculture were inhibited while levels of p-JNK and p-IRE1 remained unchanged.
IH, the hallmarker of OSAHS, could disturb insulin signaling via activating PERK/eIF2α.
阻塞性睡眠呼吸暂停低通气综合征（OSAHS）与糖代谢异常有关。目前，内质网（ER）应激已成为2型糖尿病（T2DM）发生发展的重要机制。然而，间歇性缺氧（IH）是否能诱导内质网应激，进而导致糖代谢异常仍不清楚。因此，在本研究中，我们探讨了IH条件下胰岛素信号通路的变化以及内质网应激在这些变化中的作用。
将HepG2细胞分别置于常氧（RA）或间歇性缺氧环境中8小时、16小时和24小时。间歇性缺氧组的氧气浓度每5分钟在21%至1%之间动态循环，而常氧组则保持在21%。在细胞培养基中加入胰岛素以检测AKT和磷酸化AKT（p-AKT）。在另一组实验中，HepG2细胞在暴露于间歇性缺氧或常氧之前先用4-苯基丁酸（4-PBA）进行预培养。通过蛋白质免疫印迹法检测AKT、p-AKT、磷酸化c-Jun氨基末端激酶（p-JNK）、磷酸化肌醇需求酶1（p-IRE1）、磷酸化蛋白激酶R样内质网激酶（p-PERK）和磷酸化真核翻译起始因子2α（p-eIF2α）的表达。
与常氧组相比，即使在胰岛素处理的情况下，间歇性缺氧24小时的HepG2细胞中p-AKT的表达仍显著降低。p-JNK、p-IRE1、活化转录因子6（ATF6）、p-PERK和p-eIF2α的表达上调。在间歇性缺氧条件下经4-PBA预培养的HepG2细胞中，p-AKT水平得以恢复。在经4-PBA预培养的间歇性缺氧组HepG2细胞中，p-PERK和p-eIF2α的表达受到抑制，而p-JNK和p-IRE1的水平保持不变。
间歇性缺氧作为阻塞性睡眠呼吸暂停低通气综合征的标志性特征，可通过激活PERK/eIF2α干扰胰岛素信号通路。
