Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
Mol Cell Endocrinol. 2022 Aug 20;554:111709. doi: 10.1016/j.mce.2022.111709. Epub 2022 Jul 1.
Juvenile rainbow trout (Oncorhynchus mykiss) develop social hierarchies when competing for resources in a constrained environment. Among the physiological consequences of social status are changes in organismal energy metabolism, which generally favour anabolic pathways in dominant fish and catabolic pathways in subordinate fish. The somatotropic axis is an important regulator of metabolism and growth that could be involved in mediating metabolic changes in response to social status in juvenile rainbow trout. Here we used juvenile trout housed either in dyads or individually (sham controls) to determine whether social status changes indices of somatotropic axis function. Although pituitary growth hormone expression (gh1 and gh2) did not differ among groups, circulating growth hormone (GH) increased ∼12-fold in subordinate fish compared to sham and dominant fish. Social status caused consistent differential expression of GH receptor paralogues in liver and muscle, two principal target tissues of GH. Compared to dominant and/or sham fish, ghra paralogue expression (ghra1 and ghra2) was lower, while ghrb1 expression was higher in subordinate fish. Across tissues, ghra paralogue expression was generally positively correlated with expression of insulin growth factors (igf1, igf2), while ghrb1 expression was positively correlated with transcript abundance of hormone sensitive lipase (hsl1). Because igf and hsl expression are subject to context-dependent GH control in rainbow trout, these results suggest that increased circulating GH in conjunction with differential expression of ghr paralogues may translate into prioritization of downstream catabolic lipolytic pathways in subordinate rainbow trout. These findings support a social context-dependent role for GH signalling in mediating metabolic changes in juvenile rainbow trout.
幼年虹鳟（Oncorhynchus mykiss）在资源有限的环境中竞争时会形成社会等级制度。社会地位的生理后果之一是机体能量代谢的变化，通常有利于优势鱼的合成代谢途径和从属鱼的分解代谢途径。生长激素轴是代谢和生长的重要调节剂，它可能参与调节幼年虹鳟对社会地位的代谢变化。在这里，我们使用分别饲养在成对（对照组）或单独饲养（假手术对照）的幼年虹鳟来确定社会地位是否会改变生长激素轴功能的指标。尽管垂体生长激素表达（gh1 和 gh2）在各组之间没有差异，但与假手术和优势鱼相比，从属鱼的循环生长激素（GH）增加了约 12 倍。社会地位导致肝脏和肌肉中 GH 受体同工型的一致差异表达，肝脏和肌肉是 GH 的两个主要靶组织。与优势鱼和/或假手术鱼相比，ghra 同工型表达（ghra1 和 ghra2）较低，而 ghrb1 表达在从属鱼中较高。在整个组织中，ghra 同工型表达通常与胰岛素生长因子（igf1、igf2）的表达呈正相关，而 ghrb1 表达与激素敏感脂肪酶（hsl1）的转录丰度呈正相关。由于 igf 和 hsl 的表达在虹鳟中受到 GH 控制的上下文依赖性的影响，这些结果表明，循环 GH 的增加以及 ghr 同工型的差异表达可能导致从属虹鳟下游分解代谢脂肪分解途径的优先化。这些发现支持 GH 信号在介导幼年虹鳟代谢变化中的社会背景依赖性作用。
