Albalat A, Saera-Vila A, Capilla E, Gutiérrez J, Pérez-Sánchez J, Navarro I
Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, Barcelona, E-0807, Spain.
Comp Biochem Physiol B Biochem Mol Biol. 2007 Oct;148(2):151-9. doi: 10.1016/j.cbpb.2007.05.004. Epub 2007 May 18.
Lipoprotein lipase (LPL) is a key enzyme in lipoprotein metabolism by virtue of its capacity to hydrolyze triglycerides circulating in the form of lipoprotein particles. Here we analyzed the fasting effects of LPL in gilthead sea bream (Sparus aurata) and also present the first study in fish of the role of insulin as a potential modulator of both LPL activity and expression. Fasting for 2 weeks provoked a clear decrease in adipose tissue LPL activity, concomitant with lower levels of plasma insulin, while no effects were observed in red muscle. To elucidate the specific role of insulin, increases of plasma insulin were experimentally induced by arginine and insulin injections. However, arginine predominantly stimulated glucagon over insulin secretion in this fish species while LPL activity did not change significantly in adipose tissue. Instead, insulin administration induced an increase in adipose tissue LPL activity 3 h after the injection, whereas LPL activity in red muscle was not affected. Changes in LPL activity were accompanied by an increase in LPL mRNA levels in the adipose tissue of insulin-injected gilthead sea bream, although changes in LPL expression were delayed in time with respect to variations in LPL activity. Finally, LPL mRNA levels in red muscle were similar between control and insulin-injected gilthead sea bream, suggesting that insulin does not play a direct role in the regulation of LPL in this tissue. The current study shows that LPL activity is regulated by nutritional condition and underscores the importance of insulin as a modulator of LPL activity and expression in the adipose tissue of gilthead sea bream.
脂蛋白脂肪酶（LPL）是脂蛋白代谢中的关键酶，因为它能够水解以脂蛋白颗粒形式循环的甘油三酯。在此，我们分析了禁食对金头鲷（Sparus aurata）中LPL的影响，并首次在鱼类中研究了胰岛素作为LPL活性和表达潜在调节因子的作用。禁食2周导致脂肪组织LPL活性明显下降，同时血浆胰岛素水平降低，而在红肌中未观察到影响。为了阐明胰岛素的具体作用，通过注射精氨酸和胰岛素实验性地诱导血浆胰岛素升高。然而，在这种鱼类中，精氨酸主要刺激胰高血糖素分泌而非胰岛素分泌，同时脂肪组织中的LPL活性没有显著变化。相反，注射胰岛素后3小时，脂肪组织中的LPL活性增加，而红肌中的LPL活性未受影响。LPL活性的变化伴随着胰岛素注射的金头鲷脂肪组织中LPL mRNA水平的增加，尽管LPL表达的变化在时间上相对于LPL活性的变化有所延迟。最后，对照和胰岛素注射的金头鲷红肌中的LPL mRNA水平相似，这表明胰岛素在该组织中对LPL的调节不发挥直接作用。当前研究表明LPL活性受营养状况调节，并强调了胰岛素作为金头鲷脂肪组织中LPL活性和表达调节因子的重要性。
