Apelin plays pivotal roles in fluid homeostasis, food intake and energy metabolism in mammals. However, the regulatory role of apelin in glucose metabolism in teleosts is still unclear. In this study, we investigated the regulatory role of Pyr-apelin-13 in glucose metabolism of common carp (Cyprinus carpio L.). The results showed that apelin mRNA abundance was significantly increased in the foregut and hepatopancreas after glucose injection. Insulin and glucagon also up-regulated apelin mRNA levels in the foregut, hepatopancreas and hepatocytes. In vivo, intraperitoneal injection of Pyr-apelin-13 induced hypoglycaemia through the up-regulation of mRNA expression and activity of hexokinase (HK) coupled with the down-regulation of mRNA expression and activity of glucose-6-phosphatase (G6Pase) in the hepatopancreas. In vitro, upon incubation of the primary hepatocytes with Pyr-apelin-13 (0, 10, 100 and 1000 nM), the mRNA expression of glucokinase (GK) was increased, whereas the mRNA expression of phosphoenolpyruvate carboxykinase (PEPCK) and G6Pase was reduced. For glucose transport, the glucose transporter 2 (GLUT2) mRNA expression increased in the hepatopancreas, intestine, primary enterocytes and hepatocytes after Pyr-apelin-13 treatment. Collectively, our data may provide a basis for further studies on elucidation of the role and mechanism of apelin in glucose metabolism of teleosts.

中文翻译：

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apelin在调节鲤鱼(Cyprinus carpio L.)糖代谢中的作用

Apelin 在哺乳动物的体液稳态、食物摄入和能量代谢中起着关键作用。然而，apelin 在硬骨鱼葡萄糖代谢中的调节作用仍不清楚。在这项研究中，我们研究了 Pyr-apelin-13 在鲤鱼 ( Cyprinus carpio L.)葡萄糖代谢中的调节作用。结果表明，注射葡萄糖后前肠和肝胰腺中apelin mRNA丰度显着增加。胰岛素和胰高血糖素还上调了前肠、肝胰腺和肝细胞中的apelin mRNA 水平。在体内, 腹腔注射 Pyr-apelin-13 通过上调己糖激酶 (HK) 的 mRNA 表达和活性以及下调肝胰腺中 6-磷酸酶 (G6Pase) 的 mRNA 表达和活性来诱导低血糖。在体外，在与PYR-Apelin水平-13（0，10，100和1000纳米）的原代肝细胞的孵育后，葡萄糖激酶（mRNA表达GK）增加，而磷酸烯醇丙酮酸羧（mRNA的表达PEPCK）和葡萄糖-6-磷酸酶是减少。对于葡萄糖转运，葡萄糖转运蛋白2 ( GLUT2) Pyr-apelin-13 处理后，肝胰腺、肠、原代肠细胞和肝细胞中的 mRNA 表达增加。总的来说，我们的数据可以为进一步研究阐明apelin在硬骨鱼葡萄糖代谢中的作用和机制提供基础。