Jiang H, Ge X
Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg 24060.
J Anim Sci. 2014 Jan;92(1):21-9. doi: 10.2527/jas.2013-7095. Epub 2013 Oct 28.
Growth hormone, also called somatotropin (ST), is a polypeptide hormone produced by the anterior pituitary. The major functions of GH include stimulating bone and skeletal muscle growth, lipolysis, milk production, and expression of the IGF-I gene in the liver. Based on these functions, recombinant bovine ST (bST) and recombinant porcine ST (pST) have been used to improve milk production in dairy cows and lean tissue growth in pigs, respectively. However, despite these applications, the mechanisms of action of GH are not fully understood. Indeed, there has been a lot of controversy over the role of liver-derived circulating IGF-I and locally produced IGF-I in mediating the growth-stimulatory effect of GH during the last 15 yr. It is in this context that we have conducted studies to further understand how GH stimulates skeletal muscle growth in cattle. Our results do not support a role of skeletal muscle-derived IGF-I in GH-stimulated skeletal muscle growth in cattle. Our results indicate that GH stimulates skeletal muscle growth in cattle, in part, by stimulating protein synthesis in muscle through a GH receptor-mediated, IGF-I-independent mechanism. In this review, besides discussing these results, we also argue that liver-derived circulating IGF-I should be still considered as the major mechanism that mediates the growth-stimulatory effect of GH on skeletal muscle in cattle and other domestic animals.
生长激素，也称为促生长激素（ST），是一种由垂体前叶产生的多肽激素。生长激素的主要功能包括刺激骨骼和骨骼肌生长、脂肪分解、产奶以及肝脏中IGF-I基因的表达。基于这些功能，重组牛生长激素（bST）和重组猪生长激素（pST）已分别用于提高奶牛的产奶量和猪的瘦肉组织生长。然而，尽管有这些应用，但生长激素的作用机制尚未完全了解。事实上，在过去15年里，关于肝脏来源的循环IGF-I和局部产生的IGF-I在介导生长激素的生长刺激作用中的作用一直存在很多争议。正是在这种背景下，我们进行了研究，以进一步了解生长激素如何刺激牛的骨骼肌生长。我们的结果不支持骨骼肌来源的IGF-I在生长激素刺激牛骨骼肌生长中的作用。我们的结果表明，生长激素刺激牛骨骼肌生长，部分是通过一种生长激素受体介导的、不依赖IGF-I的机制刺激肌肉中的蛋白质合成来实现的。在这篇综述中，除了讨论这些结果外，我们还认为肝脏来源的循环IGF-I仍应被视为介导生长激素对牛和其他家畜骨骼肌生长刺激作用的主要机制。
