脂毒性和糖脂毒性是2型和移植后糖尿病患者β细胞衰竭的主要触发因素。因为高尔基体是β细胞等分泌细胞中的重要细胞器,其在应激条件下的行为决定了细胞的功能能力。
为了模拟脂毒性和糖脂毒性作为β细胞衰竭的代谢应激,用棕榈酸处理大鼠胰岛素瘤INS-1E细胞,葡萄糖,或者两者兼而有之。在5.0、16.7或33mM葡萄糖存在下,在有或没有0.5mM棕榈酸的情况下培养细胞8、16、24和48小时。在存在3种浓度的葡萄糖中的任一种与0.5mM棕榈酸的情况下孵育提供了糖脂毒性。除了内质网应激标志物(Hspa5),我们评估了在实验性代谢应激下高尔基体功能的变化。在这样做的时候,我们测量了编码高尔基结构蛋白(Acbd3,Golga2和Arf1)的基因的表达水平,高尔基糖基化酶唾液酸转移酶10和唾液酸转移酶1(St3gal1),和高尔基应激介质(Creb3和Arf4)。
高尔基体通过增加St3gal1(在两种条件下P=.05)和Creb3(分别为P=.022和P=.01)的表达来响应脂毒性和糖脂毒性。Arf4基因转录物也在糖脂毒性培养基中增加(P=.03)。单独的葡萄糖毒性不诱导Creb3和Arf4的转录水平的变化。脂毒性和糖脂毒性诱导的Creb3和Arf4表达,它们是导致细胞凋亡的重要高尔基体应激反应介质。
这项初步研究表明,高尔基体应激反应在β细胞衰竭的脂毒性和糖脂毒性条件下很重要。解决导致β细胞功能障碍的细胞内分子机制之谜对于了解移植后糖尿病的病理生理学以及很可能的长期内胰岛移植失败至关重要。
Lipotoxicity and glucolipotoxicity are among the mostimportanttriggers of beta-cell failure in patients with type 2 and posttransplant diabetes. Because the Golgi apparatus is a vital organelle in secretory cells like beta cells, its behavior under stress conditions determines the cell\'s functional capacity.
To mimic lipotoxicity and glucolipotoxicity as metabolic stresses for beta-cell failure, rat insulinoma INS-1E cells were treated with palmitic acid, glucose, or both. Cells were cultured in the presence of 5.0, 16.7, or 33 mM glucose with or without 0.5 mM palmitic acid for 8, 16, 24, and 48 hours. Incubation in the presence of any of the 3 concentrations of glucose with 0.5 mM palmitic acid provided glucolipotoxicity. In addition to the endoplasmic reticulum stress marker (Hspa5), we evaluated changes in Golgi function under experimental metabolic stresses. In doing this, we measured expression levels of the genes coding Golgi structural proteins (Acbd3,Golga2, and Arf1), Golgi glycosylation enzymes sialyltransferaz10 and sialyltransferase 1 (St3gal1), and Golgi stress mediators (Creb3 and Arf4).
Golgi responded to lipotoxicity and glucolipotoxicity by increasing the expression of St3gal1 (P = .05 in both conditions) and Creb3 (P = .022 and P = .01, respectively). The Arf4 gene transcript also increased in glucolipotoxic media (P = .03). Glucotoxicity alone did not induce a change in the transcript levels of Creb3 and Arf4. Lipotoxicity and glucolipotoxicity induced Creb3 and Arf4 expression, which are important Golgi stress response mediators leading to apoptosis.
This preliminary
study showed that the Golgi stress response is important in lipotoxic and glucolipotoxic conditions in terms of beta-cell failure. Solving the mystery of intracellular molecular mechanisms leading to beta-cell dysfunction is crucial to understanding the pathophysiology of posttransplant diabetes and most probably the failure of intraportal islet transplants in the long term.