Reduction in voltage-gated K+ currents in primary cultured rat pancreatic β-cells by linoleic acids
Reduction in voltage-gated K+ currents in primary cultured rat pancreatic β-cells by linoleic acids
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DOI：
10.1210/en.2005-0225
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发表时间：
2006-02-01
期刊：
影响因子：
4.8
通讯作者：
Chen, C
中科院分区：
文献类型：
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作者：
Feng, DD;Luo, ZQ;Chen, C
除葡萄糖外，游离脂肪酸（FFA）已显示可通过胰腺β细胞中的G蛋白偶联受体（GPCR）40受体刺激胰岛素释放。游离脂肪酸可使β细胞内游离钙浓度（[Ca 2 +]（i））升高，但[Ca 2 +]（i）升高的机制尚不清楚。在这项研究中，我们研究了亚油酸对电压门控K+电流的作用。对鉴定的大鼠β细胞进行制霉菌素穿孔记录。在硝苯地平，河豚毒素，甲苯磺丁脲的存在下，电压门控K+电流进行了观察。瞬态电流占总K+电流的5%以下，而延迟整流器电流占总K+电流的95%以上。长链不饱和FFA，亚油酸（10 μ M），可逆地降低K+电流的幅度（小于10%）。cAMP/蛋白激酶A系统抑制剂H89（1 μ M）和Rp-cAMP（10 μ M）可消除这种降低，但不受蛋白激酶C抑制剂的影响。此外，forskolin和8 '-bromo-cAMP诱导的K+电流的减少与亚油酸引起的类似。亚油酸还增加β细胞中胰岛素分泌和cAMP积累。亚油酸甲酯与亚油酸具有相似的结构，但对GPR 40没有结合亲和力，不改变K+电流。用GPR 40特异性小干扰RNA处理培养的细胞可显著降低亚油酸诱导的K+电流的降低，而cAMP诱导的K+电流的降低不受影响。我们得出结论，亚油酸通过GPR 40和cAMP-蛋白激酶A系统降低大鼠β细胞中的电压门控K+电流，导致[Ca 2 +]（i）和胰岛素分泌增加。
Free fatty acids (FFAs), in addition to glucose, have been shown to stimulate insulin release through the G protein-coupled receptor (GPCR) 40 receptor in pancreatic beta-cells. Intracellular free calcium concentration ([Ca2+](i)) in beta-cells is elevated by FFAs, although the mechanism underlying the [Ca2+](i) increase is still unknown. In this study, we investigated the action of linoleic acid on voltage-gated K+ currents. Nystatin-perforated recordings were performed on identified rat beta-cells. In the presence of nifedipine, tetrodotoxin, and tolbutamide, voltage-gated K+ currents were observed. The transient current represents less than 5%, whereas the delayed rectifier current comprises more than 95%, of the total K+ currents. A long-chain unsaturated FFA, linoleic acid (10 mu M), reversibly decreased the amplitude of K+ currents (to less than 10%). This reduction was abolished by the cAMP/protein kinase A system inhibitors H89 (1 mu M) and Rp-cAMP (10 mu M) but was not affected by protein kinase C inhibitor. In addition, forskolin and 8'-bromo-cAMP induced a similar reduction in the K+ current as that evoked by linoleic acid. Insulin secretion and cAMP accumulation in beta-cells were also increased by linoleic acid. Methyl linoleate, which has a similar structure to linoleic acid but no binding affinity to GPR40, did not change K+ currents. Treatment of cultured cells with GPR40-specific small interfering RNA significantly reduced the decrease in K+ current induced by linoleic acid, whereas the cAMP-induced reduction of K+ current was not affected. We conclude that linoleic acid reduces the voltage-gated K+ current in rat beta-cells through GPR40 and the cAMP-protein kinase A system, leading to an increase in [Ca2+](i) and insulin secretion.