Palmitate-induced Ca2+-signaling in pancreatic beta-cells
Palmitate-induced Ca2+-signaling in pancreatic beta-cells
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DOI：
10.1016/j.mce.2003.09.026
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发表时间：
2003-12-30
影响因子：
4.1
通讯作者：
Schöfl, C
中科院分区：
文献类型：
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作者：
Remizov, O;Jakubov, R;Schöfl, C
已经提出游离脂肪酸（FFA）参与调节胰腺β细胞（β细胞）的胰岛素释放。由于胞浆游离Ca 2+（[Ca 2 +]（i））的升高是刺激胰岛素分泌的关键事件，因此研究了饱和FFA对[Ca 2 +]（I）的影响。棕榈酸盐用作参比化合物，并在单一fura-2负载的HIT-T15和原代小鼠β细胞中测量[Ca 2 +]（i）。用棕榈酸盐（100 μ m）刺激单个β细胞引起重复的Ca 2+瞬变或[Ca 2 +]（i）的平台样升高。在HIT-T15和小鼠β-细胞中，棕榈酸盐响应细胞的数量和棕榈酸盐诱导的Ca 2 +-信号的幅度依赖于细胞外葡萄糖浓度。在无钙培养基棕榈酸酯（100 μ M）造成只有1或2个Ca 2+瞬变表明动员Ca 2+从内部存储。撤回外部Ca 2+，电压敏感性Ca 2+通道（VSCC）阻断剂，以及K-ATP-通道开放剂二氮嗪（100 μ M）可逆地阻断棕榈酸诱导的胞浆Ca 2+反应。这表明，Ca 2+内流通过VSCC的L型耦合到膜去极化通过关闭K-ATP通道是至关重要的持续的Ca 2+信号响应棕榈酸。甲基棕榈酸酯（100 μ M）和2-溴棕榈酸酯（100 μ M），这两个抑制运输的酰基辅酶A进入线粒体，可逆地阻断棕榈酸诱导的Ca 2+信号在HIT-T15以及在原代小鼠β细胞。相比之下，浅蓝菌素（100 μ M），一种蛋白酰化的抑制剂，对棕榈酸诱导的[Ca 2 +]（i）变化没有影响，这表明线粒体棕榈酸代谢是引发Ca 2+信号所必需的。同时测量[Ca 2 +]（i）和线粒体膜电位（Deltapsi）揭示了棕榈酸盐诱导的Deltapsi去极化，这表明棕榈酸盐不增强线粒体ATP产生。因此，除了ATP之外的线粒体信号似乎是由棕榈酸代谢产生的，棕榈酸代谢是胰腺p细胞中棕榈酸诱导的Ca 2+信号的基础。(C)2003爱思唯尔爱尔兰有限公司保留所有权利。
Free fatty acids (FFA) have been proposed to participate in the regulation of insulin release from pancreatic beta-cells (beta-cells). As a rise in cytosolic free Ca2+ ([Ca2+](i)) is a key event for the stimulation of insulin secretion, the effects of saturated FFA on [Ca2+](I) were investigated. Palmitate was used as a reference compound and [Ca2+](i) was measured in single fura-2 loaded HIT-T15 and in primary mouse beta-cells. Stimulation of single beta-cells with palmitate (100 mum) caused either repetitive Ca2+ transients or a plateau-like rise in [Ca2+](i). In HIT-T15 and in mouse beta-cells, the number of palmitate-responsive cells, and the amplitude of the palmitate-induced Ca2+-signals were dependent on the extracellular glucose concentration. In Ca2+-free medium palmitate (100 muM) caused only 1 or 2 Ca2+ transients indicating mobilization of Ca2+ from internal stores. Withdrawal of external Ca2+, the addition of voltage-sensitive Ca2+ channel (VSCC) blockers, as well as the K-ATP-channel opener diazoxide (100 muM) reversibly blocked the palmitate-induced cytosolic Ca2+ responses. This demonstrates that Ca2+ influx through VSCC of the L-type coupled to membrane depolarization through closure of K-ATP-channels are crucial for a sustained Ca2+-signal in response to palmitate. Methyl palmoxirate (100 muM) and 2-bromopalmitate (100 muM), which both inhibit transport of acyl-CoA into the mitochondria, reversibly blocked the palmitate-induced Ca2+-signals in HIT-T15 as well as in primary mouse beta-cells. By contrast, cerulenin (100 muM), an inhibitor of protein acylation, had no effect on the palmitate-induced changes in [Ca2+](i), which suggests that mitochondrial palmitate metabolism is required for eliciting the Ca2+-signals. Simultaneous measurement of [Ca2+](i) and the mitochondrial membrane potential (Deltapsi) revealed palmitate-induced depolarization of Deltapsi which demonstrates that palmitate does not enhance mitochondrial ATP production. Therefore mitochondrial signals other than ATP appear to be generated from palmitate metabolism that underly the palmitate-induced Ca2+-signals in pancreatic p-cells. (C) 2003 Elsevier Ireland Ltd. All rights reserved.