Chronic Exposure to Proline Causes Aminoacidotoxicity and Impaired Beta-Cell Function: Studies In Vitro.
Chronic Exposure to Proline Causes Aminoacidotoxicity and Impaired Beta-Cell Function: Studies In Vitro.
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DOI：
10.1900/rds.2016.13.66
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发表时间：
2016-01-01
期刊：
影响因子：
--
通讯作者：
Hermansen, Kjeld
中科院分区：
文献类型：
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作者：
Liu, Zhenping;Jeppesen, Per B;Hermansen, Kjeld
背景技术背景：胰岛细胞功能障碍是糖尿病发展的标志，但原发性β细胞缺陷的原因仍然难以捉摸。在患有胰岛素抵抗、肥胖和2型糖尿病的受试者中发现循环脯氨酸水平升高。因此，我们评估β-细胞功能，基因表达，和细胞死亡后，长期暴露的胰腺β-细胞过量脯氨酸在vitro.METHODS：分离的小鼠胰岛和INS-1 E细胞孵育和不过量脯氨酸。72小时后，我们检查：（1）β细胞功能，包括基础胰岛素分泌（BIS）和葡萄糖刺激的胰岛素分泌（GSIS），（2）与胰岛素基因表达相关的转录因子和参与三羧酸循环和胆固醇生物合成的酶，（3）细胞甘油三酯（TG）和胆固醇含量，（4）INS-1 E细胞的死亡和3 H胸苷掺入，结果：高剂量脯氨酸可使INS-1 E细胞和胰岛细胞的BIS升高，GSIS降低。MafA、胰岛素1和细胞色素c氧化酶亚基VIa多肽2 mRNA表达均下调，表明脯氨酸损害胰岛素基因转录和线粒体氧化磷酸化。相反，甲羟戊酸脱羧酶基因表达上调，同时，INS-1 E细胞中的胆固醇含量增加。INS-1 E细胞的蛋白质分析显示，胞浆非特异性二肽酶和α烯醇化酶的差异expressed.CONCLUSIONS：我们的研究结果表明，脯氨酸诱导的胰岛素转录和线粒体氧化磷酸化损伤可能有助于β细胞功能障碍观察到2型糖尿病。在解释脯氨酸的病理生理作用时应谨慎，因为实验中使用了非常高的脯氨酸浓度。
BACKGROUND: Pancreatic islet-cell dysfunction is a hallmark in the development of diabetes, but the reasons for the primary beta-cell defect are still elusive. Elevated circulating proline levels have been found in subjects with insulin resistance, obesity, and type 2 diabetes. Therefore, we assessed beta-cell function, gene expressions, and cell death after long-term exposure of pancreatic beta-cells to excess proline in vitro.METHODS: Isolated mouse islets and INS-1E cells were incubated with and without excess proline. After 72 h, we examined: (1) beta-cell function, including basal insulin secretion (BIS) and glucose-stimulated insulin secretion (GSIS), (2) transcription factors related to insulin gene expression and enzymes involved in the tricarboxylic acid cycle and cholesterol biogenesis, (3) cellular triglycerides (TG) and cholesterol content, (4) the death of INS-1E cells and 3H thymidine incorporation, and (5) protein expression of INS-1E cells in response to proline by proteomics.RESULTS: We found that high doses of proline increased BIS and decreased GSIS in both isolated mouse islets and INS-1E cells. MafA, insulin 1, and the cytochrome c oxidase subunit VIa polypeptide 2 mRNA expressions were all downregulated, indicating that proline impaired insulin gene transcription and mitochondrial oxidative phosphorylation. In contrast, mevalonate decarboxylase gene expression was upregulated, and simultaneously, cholesterol content in INS-1E cells was enhanced. Protein profiling of INS-1E cells revealed that cytosolic non-specific dipeptidase and alpha enolase were differentially expressed.CONCLUSIONS: Our results indicate that proline-induced insulin transcription and mitochondrial oxidative phosphorylation impairment may contribute to the beta-cell dysfunction observed in type 2 diabetes. Caution should be applied in interpreting the pathophysiological role of proline since very high proline concentrations were used in the experiments.