Insulin and Norepinephrine Regulate Ghrelin Secretion from a Rat Primary Stomach Cell Culture
Insulin and Norepinephrine Regulate Ghrelin Secretion from a Rat Primary Stomach Cell Culture
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DOI：
10.1210/en.2012-1040
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发表时间：
2012-08-01
期刊：
影响因子：
4.8
通讯作者：
Anini, Younes
中科院分区：
文献类型：
--
作者：
Gagnon, Jeffrey;Anini, Younes
Ghrelin是一种肽类激素，主要在胃的X/A内分泌细胞中产生。广泛的研究集中在生长激素释放肽对生长激素释放和食欲调节的影响。然而，调节ghrelin分泌的机制知之甚少。在本研究中，我们建立了一个新生大鼠胃细胞的原代培养，以探讨生长激素释放肽的合成和分泌的调控机制。我们证明，该细胞制剂通过增加cAMP、细胞内钙和激活蛋白激酶C以调节的方式分泌生长素释放肽。去甲肾上腺素（NE）（0.1-10 μ M）通过增加cAMP和蛋白激酶A活性通过β 1-肾上腺素能受体刺激ghrelin分泌，而乙酰胆碱没有作用。由于循环中的ghrelin水平先前被证明与胰岛素水平呈负相关，我们研究了胰岛素对ghrelin分泌的影响。我们首先证明了生长素释放肽细胞表达胰岛素受体α和β亚基。接下来，我们确定胰岛素（1-10 nM）抑制基础和NE刺激的ghrelin分泌，导致磷酸化丝氨酸-苏氨酸激酶（AKT）增加和细胞内cAMP减少，但不改变proghrelin mRNA水平。胰岛素的抑制作用可通过抑制磷酸肌醇-3激酶和AKT而非MAPK而被阻断。较高剂量的胰岛素（100 nM）不抑制ghrelin分泌，这促使通过用100 nM胰岛素预处理细胞24 h来研究细胞胰岛素抵抗。这引起胰岛素受体表达的减少，并阻止胰岛素介导的AKT活化和生长素释放肽分泌的抑制，而对NE刺激的生长素释放肽分泌没有影响。我们的研究结果强调了交感神经系统，胰岛素和胰岛素抵抗在ghrelin分泌调节中的作用。（内分泌学153：3646-3656，2012）
Ghrelin is a peptide hormone primarily produced in the previously unidentified X/A endocrine cells of the stomach. Extensive studies have focused on the effects of ghrelin on growth hormone release and appetite regulation. However, the mechanisms regulating ghrelin secretion are less understood. In the present study, we developed a primary culture of newborn rat stomach cells to investigate the mechanisms regulating ghrelin synthesis and secretion. We demonstrated that this cell preparation secretes ghrelin in a regulated manner through the increase of cAMP, intracellular calcium, and activation of protein kinase C. Norepinephrine (NE) (0.1-10 mu M) stimulated ghrelin secretion through the beta 1-adrenergic receptor via increased cAMP and protein kinase A activity, whereas acetylcholine had no effect. Because circulating ghrelin levels were previously shown to be inversely correlated with insulin levels, we investigated the effect of insulin on ghrelin secretion. We first demonstrated that ghrelin cells express the insulin receptor alpha- and beta-subunits. Next, we determined that insulin (1-10 nM) inhibited both basal and NE-stimulated ghrelin secretion, caused an increase in phosphorylated serine-threonine kinase (AKT) and a reduction in intracellular cAMP, but did not alter proghrelin mRNA levels. The inhibitory effect of insulin was blocked by inhibiting phospho-inositol-3 kinase and AKT but not MAPK. Higher dose insulin (100 nM) did not suppress ghrelin secretion, which prompted the investigation of cellular insulin resistance by pretreating the cells with 100 nM insulin for 24 h. This caused a reduction in insulin receptor expression and prevented the insulin-mediated AKT activation and the suppression of ghrelin secretion with no impact on NE-stimulated ghrelin secretion. Our findings highlight the role of the sympathetic nervous system, insulin, and insulin resistance in the regulation of ghrelin secretion. (Endocrinology 153: 3646-3656, 2012)