Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Faculty of Life Sciences and Medicine, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, 710069, Shaanxi, P.R. China.
Shaanxi Key Laboratory of Brain Disorders & Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, 710018, Shaanxi, P.R. China.
Mol Med. 2024 Aug 13;30(1):124. doi: 10.1186/s10020-024-00889-6.
Obesity is well-established as a significant contributor to the development of insulin resistance (IR) and diabetes, partially due to elevated plasma saturated free fatty acids like palmitic acid (PA). Grb10-interacting GYF Protein 2 (GIGYF2), an RNA-binding protein, is widely expressed in various tissues including the liver, and has been implicated in diabetes-induced cognitive impairment. Whereas, its role in obesity-related IR remains uninvestigated.
In this study, we employed palmitic acid (PA) exposure to establish an in vitro IR model in the human liver cancer cell line HepG2 with high-dose chronic PA treatment. The cells were stained with fluorescent dye 2-NBDG to evaluate cell glucose uptake. The mRNA expression levels of genes were determined by real-time qRT-PCR (RT-qPCR). Western blotting was employed to examine the protein expression levels. The RNA immunoprecipitation (RIP) was used to investigate the binding between protein and mRNA. Lentivirus-mediated gene knockdown and overexpression were employed for gene manipulation. In mice, an IR model induced by a high-fat diet (HFD) was established to validate the role and action mechanisms of GIGYF2 in the modulation of HFD-induced IR in vivo.
In hepatocytes, high levels of PA exposure strongly trigger the occurrence of hepatic IR evidenced by reduced glucose uptake and elevated extracellular glucose content, which is remarkably accompanied by up-regulation of GIGYF2. Silencing GIGYF2 ameliorated PA-induced IR and enhanced glucose uptake. Conversely, GIGYF2 overexpression promoted IR, PTEN upregulation, and AKT inactivation. Additionally, PA-induced hepatic IR caused a notable increase in STAU1, which was prevented by depleting GIGYF2. Notably, silencing STAU1 prevented GIGYF2-induced PTEN upregulation, PI3K/AKT pathway inactivation, and IR. STAU1 was found to stabilize PTEN mRNA by binding to its 3'UTR. In liver cells, tocopherol treatment inhibits GIGYF2 expression and mitigates PA-induced IR. In the in vivo mice model, GIGYF2 knockdown and tocopherol administration alleviate high-fat diet (HFD)-induced glucose intolerance and IR, along with the suppression of STAU1/PTEN and restoration of PI3K/AKT signaling.
Our study discloses that GIGYF2 mediates obesity-related IR by disrupting the PI3K/AKT signaling axis through the up-regulation of STAU1/PTEN. Targeting GIGYF2 may offer a potential strategy for treating obesity-related metabolic diseases, including type 2 diabetes.
肥胖是导致胰岛素抵抗（IR）和糖尿病的重要因素，部分原因是血浆中饱和游离脂肪酸（如棕榈酸）水平升高。Grb10 相互作用 GYF 蛋白 2（GIGYF2）是一种广泛表达于肝脏等多种组织的 RNA 结合蛋白，与糖尿病引起的认知障碍有关。然而，其在肥胖相关的 IR 中的作用尚未得到研究。
在这项研究中，我们采用棕榈酸（PA）暴露在 HepG2 人肝癌细胞系中建立体外 IR 模型，用高剂量慢性 PA 处理。用荧光染料 2-NBDG 染色评估细胞葡萄糖摄取。实时 qRT-PCR（RT-qPCR）测定基因的 mRNA 表达水平。采用 Western blot 检测蛋白表达水平。采用 RNA 免疫沉淀（RIP）检测蛋白与 mRNA 的结合。采用慢病毒介导的基因敲低和过表达进行基因操作。在小鼠中，建立高脂肪饮食（HFD）诱导的 IR 模型，以验证 GIGYF2 在体内调节 HFD 诱导的 IR 中的作用和作用机制。
在肝细胞中，高水平的 PA 暴露强烈触发肝 IR 的发生，表现为葡萄糖摄取减少和细胞外葡萄糖含量升高，这与 GIGYF2 的上调显著相关。沉默 GIGYF2 可改善 PA 诱导的 IR 并增强葡萄糖摄取。相反，GIGYF2 的过表达促进了 IR、PTEN 的上调和 AKT 的失活。此外，PA 诱导的肝 IR 导致 STAU1 显著增加，而 GIGYF2 的耗竭则可防止这一增加。值得注意的是，沉默 STAU1 可防止 GIGYF2 诱导的 PTEN 上调、PI3K/AKT 通路失活和 IR。STAU1 被发现通过结合其 3'UTR 来稳定 PTEN mRNA。在肝细胞中，生育酚处理抑制 GIGYF2 的表达并减轻 PA 诱导的 IR。在体内小鼠模型中，GIGYF2 敲低和生育酚给药可减轻高脂肪饮食（HFD）诱导的葡萄糖不耐受和 IR，并抑制 STAU1/PTEN 恢复 PI3K/AKT 信号。
我们的研究揭示了 GIGYF2 通过上调 STAU1/PTEN 破坏 PI3K/AKT 信号轴来介导肥胖相关的 IR。靶向 GIGYF2 可能为治疗肥胖相关代谢疾病（包括 2 型糖尿病）提供一种潜在策略。
