TSC2对肠L细胞GLP-1分泌的调控作用机制及对血糖稳态的影响研究

GLP-1 is a peptide secreted from the intestinal L cells, which could promote β cell survival. But GLP-1 secretion was markedly reduced in type 2 diabetic patients, the reason for which was not clear. TSC2, which is a tumor suppressor with GTPase-activating protein activity towards the small G-protein Rheb (Ras homologue enriched in brain), could inhibit Rheb-mediated TOR kinase activation as a critical negative regulator of mTORC1 (mammalian target of rapamycin complex 1), a functional complex of TOR protein. There were studies shown that activation of TSC2 expression may participate in regulating L cell formation, and suppression of TSC2 could stimulate insulin secretion from β cells, but there were no studies suggesting that TSC2 is involved in the regulation of GLP-1 secretion and glucose homeostasis. In this study, we will investigate the influence of TSC2 expression on GLP-1 secretion, glucose metabolism, cell vitality，mitochondrial function and TSC2-TOR signal pathway in enteroendocrine cell-specific TSC2 knockout and knock-in mice, NCI-H716 and STC-1 cells, so as to define how TSC2 participates in the regulation of GLP-1 secretion and glucose homeostasis. In spite of this, in order to clarify the effect of TSC2 in the occurrence of diabetes, we will also observe the variation of key proteins involved in TSC2-TOR signal pathway and relative regulatory pathway in the spontaneous type 2 diabetic KKAy mice, and study the influence of glucotoxicity and lipotoxicity on GLP-1 secretion and relative mechanisms in NCI-H716 and STC-1 cells. Through the study, we wish to supply experimental basis for the study of pathogenesis of diabetes, and novel thinking and targets for the development of anti-diabetic drugs.

GLP-1是肠L细胞分泌的一种多肽，具有显著的β细胞保护功能。糖尿病患者中GLP-1分泌明显减少，但原因不明。TSC2是一种肿瘤抑制蛋白，具有GTP酶激活蛋白活性，是TOR蛋白重要的负调控因子，在L细胞形成和胰岛素分泌中具有重要作用。目前尚未见有关TSC2参与GLP-1分泌和血糖稳态调控的报道。本课题将分别采用肠内分泌细胞TSC2特异性敲除和敲入小鼠以及L细胞株NCI-H716和STC-1，考察TSC2表达变化对GLP-1分泌、糖稳态、细胞活力、线粒体功能以及TSC2-TOR信号通路的影响，阐明TSC2如何参与调节GLP-1分泌和糖稳态；同时考察2型糖尿病KKAy小鼠中TSC2-TOR信号通路及调控通路中关键蛋白的变化，研究"糖脂毒性"对两种L细胞中GLP-1分泌的影响和机制，阐明TSC2在糖尿病发生中的作用，从而为糖尿病的发病机制研究提供实验依据，为抗糖尿病药物的研发提供新思路和新靶点。