IGF-I/PI3K信号通路在糖尿病胃轻瘫发病中的作用及其机制

Gastroparesis is one of most common chronic complications of diabetes that may seriously affect every-day life of the patients. Research has shown that insulin and IGF-I levels were significantly decreased in blood of diabetic animal;Model animals have suggested gastroparesis can significantly decrease the activity of PKC signaling pathway in gastric smooth muscles,accomplished by increasing the cAMP concentration. Our previous study on rats further indicates that besides cAMP, cGMP concentration is also increased sharply. And at the same time, PDE expression is inhibited. Recent researches indicated that IGF-I can adjust the PKC and PDE pathway activities through controlling the PI3K/Akt signal pathway. However, The PI3K-Akt signal pathway has not been reported in diabetic gastroparesis process.Therefore, here we propose to employ STZ-induced diabetes rats as model target to investigate whether and how IGF-I/PI3K participates the processes that decrease the activities of PKC and PDE pathway. In detail, molecular biology, immunohistochemistry, and electrophysiology will be combined to verify the hypothesis that IGF-I/PI3K slows down the motility of gastric smooth muscle by inhibiting the downstream PKC/IP4/Ca2+ and PDE/cGMP/cAMP pathway signal. This proposal has great scientific significance and application potential in revealing the pathogenesis of gastroparesis and preventing and treating diabetes.

胃轻瘫是糖尿病常见的慢性并发症之一，严重影响患者的生活质量。研究表明，糖尿病动物血液中胰岛素和IGF-I的水平均明显下降；在糖尿病胃轻瘫模型动物胃平滑肌PKC通路活性明显下调，而cAMP水平明显升高；我们的前期结果表明，糖尿病大鼠胃平滑肌cGMP水平也明显升高，并伴有PDE表达明显减少。IGF-I可通过PI3K/Akt调节PKC、PDE通路活性，但IGF-I/PI3K在糖尿病胃轻瘫发病过程中的作用至今未见报道。因此，本研究拟以STZ诱导的糖尿病大鼠为研究对象，采用分子生物学、免疫组织化学、电生理学等技术，探讨IGF-I/PI3K是否参与在糖尿病引起的胃平滑肌PKC和PDE下调过程及其机制，阐明糖尿病发展过程中IGF-I/PI3K通过抑制下游的PKC和PDE/cGMP/cAMP通路，引起胃轻瘫的机理。本研究对揭示糖尿病胃轻瘫发病机理以及临床防治糖尿病胃轻瘫具有重要的理论意义和潜在的应用价值。

糖尿病胃轻瘫（Diabitic Gastroparesis，DGP）是常见的糖尿病消化道并发症之一，可导致机体血糖波动大、药物控制乏力，进而加速相关糖尿病急慢性并发症发生。因此探讨DGP相关发生机制及干预措施，对于临床探索新的治疗方案至关重要。IGF-1作为多功能细胞调控因子，可通过PI3K-Akt调节PKC、PDE及多种细胞行为。为了阐明IGF-1-PI3K在DGP发生过程中的作用，我们进行了深入研究。首先，我们研究了在DGP发生过程中IGF-1-PI3K通路及相关细胞凋亡、自噬、内质网应激的变化，其次我们又研究了CNP-NPR-B/pGC-cGMP、PI3K-AKT-mTOR、AMPK-mTOR的变化规律与细胞凋亡、自噬、内质网应激的关系，最后我们在体外培养细胞中研究了IGF-1对高糖状态下细胞凋亡、自噬、内质网应激的影响及机制。本研究确定了DGP发生过程中细胞凋亡、自噬、内质网应激的变化，初步阐明IGF-1-PI3K的作用及相关分子机制；并首次提出（1）在DGP发生初期， PI3K-AKT活化mTOR作用强，弱化了AMPK抑制mTOR活性的作用；随着病程延长，PI3K-AKT活性减弱，AMPK活性增强，当糖尿病胃轻瘫确定后，mTOR表现为活性下降；（2）cGMP-PDE3-cAMP通路参与DGP发生发展，且CNP处理后组织外泌的cGMP和cAMP量增多而平滑肌组织PDE3蛋白及mRNA表达减少；（3）IGF-1通过PI3K-AKT-PKC通路介导胃平滑肌细胞内Ca2+浓度变化，参与DGP发生过程中细胞凋亡、自噬、内质网应激的变化的结论。上述研究结论能够为进一步阐明DGP的发生机制及临床治疗新方案的探索提供科学的理论依据与实验依据。