Department of Internal Medicine, Diabetes Unit, Endocrine and Metabolic Sciences and Biochemistry, University of Siena, Viale Bracci 18, 53100 Siena, Italy.
Acta Diabetol. 2012 Dec;49 Suppl 1:S123-31. doi: 10.1007/s00592-011-0368-8. Epub 2012 Jan 17.
Post-transplant diabetes mellitus represents an important complication of prolonged immunosuppressive treatment after solid organ transplantation. The immunosuppressive toxicity, responsible for a persistent impairment of glucose metabolism in pancreatic islet-transplanted patients, is mainly attributed to calcineurin inhibitors and steroids, while other immunosuppressive molecules (azathioprine and mycophenolic acid, MPA) are considered not to have a toxic effect. In the present study, in vitro effects of MPA have been investigated in mouse beta-cell lines (βTC-1 and βTC-6) and in purified human pancreatic islets. βTC-1, βTC-6, and human pancreatic islets were exposed to various concentrations of MPA for different times. Consequently, we evaluated the viability, the induction of apoptosis, the glucose-stimulated insulin secretion, and the expression of β-cell function genes (Isl1, Pax6, Glut-2, glucokinase) and apoptosis-related genes (Bax and Bcl2). βTC-1, βTC-6, and human islets treated, respectively, for 48 and 72 h with 15-30 nM MPA showed altered islet architecture, as compared with control cells. We observed for βTC-1 and βTC-6 almost 70% reduction in cell viability; three to sixfold induction of TUNEL/apoptotic-positive cells quantified by FACS analysis. A twofold increase in apoptotic cells was observed in human islets after MPA exposure associated with strong inhibition of glucose-stimulated insulin secretion. Furthermore, we showed significant down-regulation of gene expression of molecules involved in β-cell function and increase rate between Bax/Bcl2. Our data demonstrate that MPA has an in vitro diabetogenic effect interfering at multiple levels with survival and function of murine and human pancreatic β-cells.
移植后糖尿病是实体器官移植后长期免疫抑制治疗的重要并发症。导致胰岛移植患者葡萄糖代谢持续受损的免疫抑制毒性主要归因于钙调神经磷酸酶抑制剂和类固醇，而其他免疫抑制分子（硫唑嘌呤和霉酚酸，MPA）则被认为没有毒性作用。在本研究中，研究人员在小鼠β细胞系（βTC-1 和 βTC-6）和纯化的人胰岛中研究了 MPA 的体外作用。βTC-1、βTC-6 和人胰岛分别暴露于不同浓度的 MPA 不同时间。因此，评估了细胞活力、细胞凋亡诱导、葡萄糖刺激的胰岛素分泌以及β细胞功能基因（Isl1、Pax6、Glut-2、葡萄糖激酶）和凋亡相关基因（Bax 和 Bcl2）的表达。与对照细胞相比，用 15-30 nM MPA 分别处理 48 和 72 小时的βTC-1、βTC-6 和人胰岛显示出胰岛结构改变。研究人员观察到βTC-1 和βTC-6 的细胞活力降低了近 70%；通过 FACS 分析定量的 TUNEL/凋亡阳性细胞增加了 3 到 6 倍。MPA 暴露后，人胰岛中观察到凋亡细胞增加了两倍，同时葡萄糖刺激的胰岛素分泌受到强烈抑制。此外，还观察到参与β细胞功能的分子的基因表达显著下调，并且 Bax/Bcl2 之间的比率增加。研究结果表明，MPA 在体外具有致糖尿病作用，可在多个水平上干扰小鼠和人胰岛β细胞的存活和功能。
