mTORC2/CTGF信号通路在肠促胰岛素类似物诱导胰腺慢性纤维化损伤分子机制研究

Incretin mimetics are newly discovered as a type of widely used hypoglycemic drugs. However, in recent years it has been observed that rats with long-term injection of incretin mimetics developed chronic pancreatic lesions including induction of autophagy, vacuolation and fibrosis in glandular cells. Our preliminary studies have shown that incretin mimetics could increase mTORC2 and CTGF expression, but no significant changes in TGF-β. However, the detailed mechanisms remained unclear. On literatures and our preliminary studies，autophagy may promote fibrosis by the activation of mTORC2 / CTGF. Therefore, we hypothesize that incretin mimetics induce fibrosis in pancreatic glandular cells and impair pancreatic exocrine functions by activation of autophagy and mTORC2-mediated activation of CTGF in glandular cells. In order to address the questions, we first examined incretin mimetics effect on dynamics of autophagy and fibrosis in glandular cells both in animal and cell models. Moreover, we tested the effect of incretin mimetics -induced fibrosis in glandular cells by blocking autophagy, mTORC2 and CTGF. Finally we studied the interaction between GLP-1R, mTORC2 and CTGF to roughly elucidate the mechanisms of incretin mimetics -induced chronic fibrotic lesions in pancreas and to shed light on the potential risk of clinical application of incretin mimetics.

肠促胰岛素类似物作为糖尿病新型治疗药物受到广泛关注。目前研究发现长期注射肠促胰岛素类似物可致胰腺腺泡细胞萎缩，腺泡细胞空泡增多，胰腺出现慢性纤维化损伤。本研究组前期研究表明肠促胰岛素类似物可引起腺泡细胞mTORC2、CTGF表达上调，但TGF-β表达却无明显改变，其机制尚不明确。结合文献和本研究组前期研究表明自噬增强有激活mTORC2/CTGF通路促进纤维化可能，因此本研究组提出如下假说：肠促胰岛素类似物长期作用可致胰腺腺泡细胞自噬加强而激活mTORC2/CTGF通路，CTGF旁分泌作用星状细胞促进CTGF表达增加，加重胰腺慢性纤维化。我们通过建立动物和细胞模型，阻断自噬、mTORC2及CTGF后观察肠促胰岛素类似物对胰腺腺泡细胞自噬和胰腺慢性纤维化影响；同时研究mTORC2、CTGF相互作用，初步阐明肠促胰岛素类似物诱导胰腺慢性纤维化损伤发生机制，为临床肠促胰岛素类似物潜在风险提供预警。

肠促胰岛素（incretin）类似物，也称为胰高血糖素样肽-1(GLP-1)受体激动剂，是一类具有多种抗高血糖作用的新型降糖药物。肠促胰岛素类似物不仅降糖效果理想，同时低血糖不良反应轻微，且具有传统降糖药物不具备的优势。然而，近年来，临床及实验研究发现肠促胰岛素类似物可能会诱发急性胰腺炎与胰腺慢性损伤，使其在临床应用蒙上阴影。本项目前期已证实长期使用艾塞那肽可导致胰腺慢性损伤，主要表现为胰腺腺泡细胞萎缩、空泡增多及间质纤维化，但具体机制尚未明确。经前期探究和文献分析，我们提出了课题假设：肠促胰岛素类似物长期作用可致胰腺腺泡细胞自噬加强而激活mTORC2/CTGF通路，CTGF旁分泌作用星状细胞促进CTGF表达增加，加重胰腺慢性纤维化。本项目通过SD大鼠长期皮下注射艾塞那肽，取其胰腺检测大鼠胰腺组织自噬和纤维化信号分子的表达，同时完成体外实验，药物干预胰腺腺泡细胞AR42J和原代星状细胞，检测体外自噬和胰腺星状细胞活化状态。课题从药物对大鼠胰腺自噬、凋亡、纤维化改变等方向进行了研究。结果显示：艾塞那肽通过结合胰腺腺泡细胞上的GLP-1R而下调LAMP-2引起细胞自噬流受阻，从而导致细胞释放CTGF，其旁分泌诱导胰腺星状细胞活化，最终导致胰腺纤维化。因此，该研究发现尽管艾塞那肽无法直接活化星状细胞，但是可通过诱导胰腺腺泡细胞分泌CTGF而间接活化胰腺星状细胞，该结果很好地解释了本课题组织前期在胰腺组织学水平的发现。