Center of Excellence for Poultry Science, University of Arkansas, 1260 W. Maple Street, Fayetteville, AR, 72701, USA.
Dipartimento Di Scienze E Tecnologie Agro-Alimentari, Alma Mater Studiorum-Università Di Bologna, Bologna, Italy.
Sci Rep. 2020 Nov 5;10(1):19191. doi: 10.1038/s41598-020-76329-2.
Orexins are originally characterized as orexigenic hypothalamic neuropeptides in mammals. Subsequent studies found orexin to be expressed and perform pleiotropic functions in multiple tissues in mammals. In avian (non-mammalian) species, however, orexin seemed to not affect feeding behavior and its physiological roles are poorly understood. Here, we provide evidence that orexin and its related receptors are expressed in chicken hepatocytes. Double immunofluorescence staining showed that orexin is localized in the ER, Golgi, and in the lysosomes in LMH cells. Brefeldin A treatment reduced orexin levels in the culture media, but increased it in the cell lysates. Administration of recombinant orexins upregulated the expression of orexin system in the liver of 9-day old chicks, but did not affect feed intake. Recombinant orexins increased fatty acid synthase (FASN) protein levels in chicken liver, activated acetyl-CoA carboxylase (ACCα), and increased FASN, ATP citrate lyase(ACLY), and malic enzyme (ME) protein expression in LMH cells. Blockade ERK1/2 activation by PD98059 attenuated these stimulating effects of orexin on lipogenic factors. Overexpression of ERK1/2 increased the expression of lipogenic genes, and orexin treatment induced the phosphorylated levels of ERK1/2, but not that of p38 or JNK1/2 in chicken liver and LMH cells. Taken together, this is the first report evidencing that orexin is expressed and secreted from chicken hepatocytes, and that orexin induced hepatic lipogenesis via activation of ERK1/2 signaling pathway.
食欲素最初被特征化为哺乳动物下丘脑的食欲肽。随后的研究发现，食欲素在哺乳动物的多种组织中表达并发挥多种功能。然而，在禽类（非哺乳动物）物种中，食欲素似乎不会影响摄食行为，其生理作用知之甚少。在这里，我们提供证据表明，食欲素及其相关受体在鸡肝细胞中表达。双免疫荧光染色显示，食欲素定位于 LMH 细胞的内质网、高尔基体和溶酶体中。布雷菲德菌素 A 处理减少了培养基中的食欲素水平，但增加了细胞裂解物中的食欲素水平。重组食欲素的给药上调了 9 日龄雏鸡肝脏中食欲素系统的表达，但不影响采食量。重组食欲素增加了鸡肝中脂肪酸合酶 (FASN) 蛋白水平，激活乙酰辅酶 A 羧化酶 (ACCα)，并增加了 FASN、三磷酸柠檬酸裂解酶 (ACLY) 和苹果酸酶 (ME) 在 LMH 细胞中的蛋白表达。用 PD98059 阻断 ERK1/2 激活减弱了食欲素对脂肪生成因子的这些刺激作用。ERK1/2 的过表达增加了脂肪生成基因的表达，食欲素处理诱导 ERK1/2 的磷酸化水平增加，但鸡肝和 LMH 细胞中 p38 或 JNK1/2 的磷酸化水平没有增加。总之，这是第一个报道表明食欲素在鸡肝细胞中表达和分泌，并且食欲素通过激活 ERK1/2 信号通路诱导肝脂肪生成。
