Hainan Provincial Key Laboratory for Tropical Hydrobiology and Biotechnology, Department of Aquaculture, Hainan University, Haikou, Hainan 570228, China.
State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou 570228, China.
Gen Comp Endocrinol. 2021 Jun 1;307:113744. doi: 10.1016/j.ygcen.2021.113744. Epub 2021 Mar 9.
The carnivorous teleost fish is often intolerant to high levels of postprandial plasma glucose. This study aimed to evaluate the effects of insulin-like growth factor-1 (IGF-1) and growth hormone (GH) administrations on plasma glucose levels and expression of glucose transporters (GLUTs) in various tissues of hybrid grouper, and hence to further clarify the hormone-GLUTs-plasma glucose regulating axis. Twenty-four experimental fish (average body weight: 77.5 ± 5.4 g) were selected and injected with recombinant human IGF-1 (0.2 μg/g body weight) and PBS (0.01 mol/L) in enterocoelia, respectively, and in the GH injected experiment, the same quantity of fish (average body weight: 103.8 ± 5.8 g) were administrated with GH at a dose of 0.5 μg/g body weight or with PBS at a dose of 0.01 mol/L. Results showed that plasma glucose level was significantly (P < 0.05) declined by the IGF-1 administration but elevated by the GH administration. Plasma IGF-1 concentration was significantly (P < 0.01) elevated by the IGF-1 administration, while GH concentration did not significantly (P ≥ 0.05) respond to the GH administration. The relative mRNA levels of insulin-like growth factor-1 receptor a (IGF-Ra) in liver and muscle were decreased significantly with the IGF-1 administration, and a similar variation tendency was also found in insulin-like growth factor-1 receptor b (IGF-Rb) in liver, muscle and adipose tissues. Besides, the relative mRNA level of insulin receptor (IRS) in liver was significantly increased in the IGF-1 administrated group. After the GH administration, the mRNA levels of hepatic growth factor receptor 2 (GHR2) and IGF-1 were significantly elevated. As for GLUTs, the relative mRNA levels of GLUT1 and GLUT2 in liver were obviously elevated by the IGF-1 administration, while the mRNA level of GLUT4 in muscle was reduced. In liver, the protein levels of GLUT1, 2 and 4 were significantly elevated by the IGF-1 administration, and in adipose, only GLUT1 was observed to have a significantly increased protein level. The mRNA expression of GLUTs was less affected by the GH administration. The protein level of GLUT1 in liver was significantly reduced by the GH administration, while in adipose, it was significantly increased. The protein level of GLUT2 in liver or adipose showed an opposite variation as that of GLUT1. Overall, IGF-1 had a hypoglycemic effect on hybrid grouper, and this probably was through up-regulating the protein levels of hepatic GLUT1, 2 and 4 and adipose GLUT1. GH showed an opposite role in regulating plasma glucose level as IGF-1.
肉食性硬骨鱼类通常不能耐受餐后高血糖。本研究旨在评估胰岛素样生长因子 1（IGF-1）和生长激素（GH）给药对杂交石斑鱼不同组织中血糖水平和葡萄糖转运体（GLUTs）表达的影响，从而进一步阐明激素-GLUTs-血糖调节轴。选择 24 条实验鱼（平均体重：77.5±5.4g），分别在内脏腔注射重组人 IGF-1（0.2μg/g 体重）和 PBS（0.01mol/L），在 GH 注射实验中，同样数量的鱼（平均体重：103.8±5.8g）以 0.5μg/g 体重的剂量给予 GH 或 0.01mol/L 的 PBS。结果表明，IGF-1 给药可显著降低（P<0.05）血糖水平，而 GH 给药则升高血糖水平。IGF-1 给药可显著升高（P<0.01）血浆 IGF-1 浓度，而 GH 浓度对 GH 给药无显著反应（P≥0.05）。肝脏和肌肉中胰岛素样生长因子 1 受体 a（IGF-Ra）的相对 mRNA 水平随着 IGF-1 给药而显著降低，肝脏、肌肉和脂肪组织中胰岛素样生长因子 1 受体 b（IGF-Rb）也出现类似的变化趋势。此外，肝脏中胰岛素受体（IRS）的相对 mRNA 水平在 IGF-1 给药组中显著升高。GH 给药后，肝生长因子受体 2（GHR2）和 IGF-1 的 mRNA 水平明显升高。对于 GLUTs，肝脏中 GLUT1 和 GLUT2 的相对 mRNA 水平随着 IGF-1 给药而明显升高，而肌肉中 GLUT4 的 mRNA 水平降低。IGF-1 给药可显著升高肝脏中 GLUT1、2 和 4 的蛋白水平，而脂肪中仅观察到 GLUT1 的蛋白水平显著升高。GH 给药对 GLUTs 的 mRNA 表达影响较小。GH 给药可显著降低肝脏中 GLUT1 的蛋白水平，而脂肪中则显著升高。肝或脂肪中 GLUT2 的蛋白水平与 GLUT1 相反。总体而言，IGF-1 对杂交石斑鱼具有降血糖作用，这可能是通过上调肝脏 GLUT1、2 和 4 以及脂肪 GLUT1 的蛋白水平来实现的。GH 在调节血糖水平方面与 IGF-1 作用相反。
