Maechler Pierre
Department of Cell Physiology and Metabolism & Faculty Diabetes Center, University of Geneva Medical Center, Geneva, Switzerland.
Diabetes Res Clin Pract. 2017 Sep;131:149-153. doi: 10.1016/j.diabres.2017.07.009. Epub 2017 Jul 12.
Pancreatic beta-cells secrete insulin in response to circulating glucose, thereby maintaining euglycemia. Inside the beta-cell, glucose is transformed into intracellular signals stimulating exocytosis. While calcium is an obligatory messenger, this ion is not sufficient to promote the full secretory response. Accordingly, glucose metabolism produces the additive factor glutamate that participates to an amplifying pathway of the calcium signal. Although intracellular glutamate potentiates insulin secretion, extracellular glutamate may activate ionotropic receptors. As a consequence of such activation, insulin exocytosis is slowed down. Therefore, for the beta-cell glutamate is a double-edged sword, an amplifying pathway and a negative feedback, illustrating the principle of homeostasis.
胰腺β细胞会根据循环中的葡萄糖分泌胰岛素，从而维持血糖正常。在β细胞内部，葡萄糖被转化为刺激胞吐作用的细胞内信号。虽然钙是必不可少的信使，但该离子不足以促进完整的分泌反应。因此，葡萄糖代谢产生了参与钙信号放大途径的附加因子谷氨酸。尽管细胞内谷氨酸会增强胰岛素分泌，但细胞外谷氨酸可能会激活离子型受体。这种激活的结果是胰岛素胞吐作用减慢。因此，对β细胞来说，谷氨酸是一把双刃剑，既是一种放大途径，也是一种负反馈，体现了稳态的原理。
