Institute of Clinical Biochemistry, Hannover Medical School, 30623 Hannover, Germany.
Diabetologia. 2011 Jul;54(7):1744-55. doi: 10.1007/s00125-011-2133-5. Epub 2011 Apr 12.
AIMS/HYPOTHESIS: Glucose is the main stimulus of insulin secretion in pancreatic beta cells. However, high glucose has also been considered to damage beta cells. In this study we examined, with special emphasis on the role of the glucose sensor enzyme glucokinase, whether elevated glucose metabolism evokes toxicity to beta cells.
RINm5F-R-EYFP-GK cells, producing glucokinase in response to a synthetic inducer, and rat beta cells were incubated at different glucose concentrations. Glucokinase enzyme activity, insulin secretion, cell viability and mitochondrial metabolism were analysed.
Glucokinase production evoked a concentration-dependent increase in glucose-induced insulin secretion from RINm5F-R-EYFP-GK cells without reducing cell viability. Pre-culture at high glucose (30 mmol/l) in the absence of high concentrations of NEFA neither reduced viability nor significantly increased apoptosis in RINm5F-R-EYFP-GK cells and rat beta cells. The integrity of the mitochondrial respiratory chain and mitochondrial dynamics, namely fusion and fission, were not impaired by high glucose pre-culture. As previously demonstrated in mouse beta cells, pre-culture at high glucose significantly decreased the mitochondrial membrane potential heterogeneity in RINm5F-R-EYFP-GK cells. Indeed, after starvation, in response to glucose, rat beta cells and RINm5F-R-EYFP-GK cells with glucokinase production pre-cultured for 48 h at high glucose showed the fastest increase in the mitochondrial membrane potential.
CONCLUSIONS/INTERPRETATION: Our experiments do not support the hypothesis that glucokinase and the glucose metabolism on its own act as a mediator of beta cell toxicity. By contrast, rather a beneficial effect on glucose-induced insulin secretion after glucokinase production was observed, based on an improved coupling of the glucose stimulus to the mitochondrial metabolism.
目的/假设：葡萄糖是胰岛β细胞胰岛素分泌的主要刺激物。然而，高葡萄糖也被认为会损害β细胞。在这项研究中，我们特别强调葡萄糖传感器酶葡萄糖激酶的作用，研究了升高的葡萄糖代谢是否会引起β细胞毒性。
用合成诱导剂产生葡萄糖激酶的 RINm5F-R-EYFP-GK 细胞和大鼠β细胞在不同葡萄糖浓度下孵育。分析葡萄糖激酶酶活性、胰岛素分泌、细胞活力和线粒体代谢。
葡萄糖激酶的产生引起了 RINm5F-R-EYFP-GK 细胞中葡萄糖诱导的胰岛素分泌的浓度依赖性增加，而不降低细胞活力。在不存在高浓度 NEFA 的情况下，高葡萄糖（30mmol/l）预培养既没有降低 RINm5F-R-EYFP-GK 细胞和大鼠β细胞的活力，也没有显著增加细胞凋亡。高葡萄糖预培养不会损害线粒体呼吸链和线粒体动力学的完整性，即融合和裂变。与之前在小鼠β细胞中证明的一样，高葡萄糖预培养显著降低了 RINm5F-R-EYFP-GK 细胞中线粒体膜电位异质性。事实上，在饥饿后，对葡萄糖的反应中，经过 48 小时高葡萄糖预培养产生葡萄糖激酶的大鼠β细胞和 RINm5F-R-EYFP-GK 细胞显示出最快的线粒体膜电位增加。
结论/解释：我们的实验不支持葡萄糖激酶和其自身的葡萄糖代谢作为β细胞毒性的介质的假设。相反，在产生葡萄糖激酶后，观察到对葡萄糖诱导的胰岛素分泌有有益的影响，这是基于改善了葡萄糖刺激与线粒体代谢的偶联。
