TRAM1 protect HepG2 cells from palmitate induced insulin resistance through ER stress-JNK pathway.
TRAM1 protect HepG2 cells from palmitate induced insulin resistance through ER stress-JNK pathway.
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DOI：
10.1016/j.bbrc.2015.01.027
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发表时间：
2015-02
影响因子：
3.1
通讯作者：
Zhuqi Tang;Wanlu Zhang;C. Wan;Guangfei Xu;Xiaoke Nie;Xiaohui Zhu;Nana Xia;Yun M. Zhao;Suxin Wang-Sux
中科院分区：
文献类型：
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作者：
Zhuqi Tang;Wanlu Zhang;C. Wan;Guangfei Xu;Xiaoke Nie;Xiaohui Zhu;Nana Xia;Yun M. Zhao;Suxin Wang-Sux
过量的血清游离脂肪酸（FFA）是胰岛素抵抗发病机制的基础。慢性内质网（ER）应激是肥胖引起的肝脏胰岛素抵抗的主要原因。通过高脂喂养 (HFD)，FFA 可以激活靶组织中的慢性内质网 (ER) 应激，启动 FFA 和胰岛素信号传导之间的负串扰。然而，胰岛素抵抗和内质网应激之间的分子联系仍有待确定。我们在这里报道了易位链相关膜蛋白 1 (TRAM1)，一种内质网驻留膜蛋白，与肝细胞胰岛素抵抗的发生有关。 TRAM1 在胰岛素抵抗肝组织和棕榈酸酯 (PA) 处理的 HepG2 细胞中显着上调。此外，我们发现 TRAM1 的缺失会导致 CHOP 和 GRP78 的过度激活，以及下游 JNK 通路的激活。鉴于 ER 应激的激活在胰岛素抵抗中发挥促进作用，因此还分析了 Akt 和 GSK-3β 的磷酸化。我们发现 TRAM1 的消耗显着减弱了细胞中 Akt 和 GSK-3β 的磷酸化。此外，与 JNK 抑制剂 SP600125 一起应用可逆转 TRAM1 干扰对 Akt 磷酸化的影响。还测定了脂滴的积累和两种关键糖异生酶 PEPCK 和 G6Pase 的表达，发现与 Akt 的磷酸化表现出类似的趋势。葡萄糖摄取测定表明，敲低 TRAM1 会增强 PA 诱导的葡萄糖摄取下调，而使用 SP600125 抑制 JNK 可以阻断 TRAM1 对葡萄糖摄取的影响。这些数据表明，TRAM1 可能通过减轻 ER 应激来保护 HepG2 细胞免受 PA 诱导的胰岛素抵抗。
Excess serum free fatty acids (FFAs) are fundamental to the pathogenesis of insulin resistance. Chronic endoplasmic reticulum (ER) stress is a major contributor to obesity-induced insulin resistance in the liver. With high-fat feeding (HFD), FFAs can activate chronic endoplasmic reticulum (ER) stress in target tissues, initiating negative crosstalk between FFAs and insulin signaling. However, the molecular link between insulin resistance and ER stress remains to be identified. We here reported that translocating chain-associated membrane protein 1 (TRAM1), an ER-resident membrane protein, was involved in the onset of insulin resistance in hepatocytes. TRAM1 was significantly up-regulated in insulin-resistant liver tissues and palmitate (PA)-treated HepG2 cells. In addition, we showed that depletion of TRAM1 led to hyperactivation of CHOP and GRP78, and the activation of downstream JNK pathway. Given the fact that the activation of ER stress played a facilitating role in insulin resistance, the phosphorylation of Akt and GSK-3β was also analyzed. We found that depletion of TRAM1 markedly attenuated the phosphorylation of Akt and GSK-3β in the cells. Moreover, application with JNK inhibitor SP600125 reversed the effect of TRAM1 interference on Akt phosphorylation. The accumulation of lipid droplets and expression of two key gluconeogenic enzymes, PEPCK and G6Pase, were also determined and found to display a similar tendency with the phosphorylation of Akt. Glucose uptake assay indicated that knocking down TRAM1 augmented PA-induced down-regulation of glucose uptake, and inhibition of JNK using SP600125 could block the effect of TRAM1 on glucose uptake. These data implicated that TRAM1 might protect HepG2 cells against PA-induced insulin resistance through alleviating ER stress.