Objective

The liver is a central target organ of growth hormone (GH), which stimulates the synthesis of insulin-like growth factor 1 (IGF1) and affects multiple biochemical pathways. A systematic multi-omics analysis of GH effects in the liver has not been performed. GH receptor (GHR) deficiency is a unique model for studying the consequences of lacking GH action. In this study, we used molecular profiling techniques to capture a broad spectrum of these effects in the liver of a clinically relevant large animal model for Laron syndrome.

Methods

We performed holistic proteome and targeted metabolome analyses of liver samples from 6-month-old GHR-deficient (GHR-KO) pigs and GHR-expressing controls (four males, four females per group).

Results

GHR deficiency resulted in an increased abundance of enzymes involved in amino acid degradation, in the urea cycle, and in the tricarboxylic acid cycle. A decreased ratio of long-chain acylcarnitines to free carnitine suggested reduced activity of carnitine palmitoyltransferase 1A and thus reduced mitochondrial import of fatty acids for beta-oxidation. Increased levels of short-chain acylcarnitines in the liver and in the circulation of GHR-KO pigs may result from impaired beta-oxidation of short-chain fatty acids or from increased degradation of specific amino acids. The concentration of mono-unsaturated glycerophosphocholines was significantly increased in the liver of GHR-KO pigs without morphological signs of steatosis, although the abundances of several proteins functionally linked to non-alcoholic fatty liver disease (fetuin B, retinol binding protein 4, several mitochondrial proteins) were increased. Moreover, GHR-deficient liver samples revealed distinct changes in the methionine and glutathione metabolic pathways, in particular, a significantly increased level of glycine N-methyltransferase and increased levels of total and free glutathione. Several proteins revealed a sex-related abundance difference in the control group but not in the GHR-KO group.

Conclusions

Our integrated proteomics/targeted metabolomics study of GHR-deficient and control liver samples from a clinically relevant large animal model identified a spectrum of biological pathways that are significantly altered in the absence of GH action. Moreover, new insights into the role of GH in the sex-related specification of liver functions were provided.

中文翻译：

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没有生长激素（GH）作用时肝脏的功能变化-GH受体缺陷型猪模型的蛋白质组学和代谢组学见解。

目的

肝脏是生长激素（GH）的主要靶器官，它可以刺激胰岛素样生长因子1（IGF1）的合成并影响多种生化途径。尚未对肝中GH的作用进行系统的多组学分析。GH受体（GHR）缺乏症是研究缺乏GH作用后果的独特模型。在这项研究中，我们使用分子谱分析技术在临床相关的大型动物Laron综合征模型的肝脏中捕获了广泛的这些作用。

方法

我们对6个月大的GHR缺陷型（GHR -KO）猪和GHR表达对照（每组四只雄性，四只雌性）的肝脏样本进行了整体蛋白质组和靶向代谢组分析。

结果

GHR缺乏导致参与氨基酸降解，尿素循环和三羧酸循环的酶含量增加。长链酰基肉碱与游离肉碱的比率降低，表明肉碱棕榈酰转移酶1A的活性降低，从而减少了线粒体脂肪酸的β氧化作用。肝脏和GHR -KO猪的循环中短链酰基肉碱水平升高可能是由于短链脂肪酸的β-氧化受损或特定氨基酸的降解增加所致。GHR肝脏中单不饱和甘油磷酸胆碱的浓度显着增加-KO猪没有脂肪变性的形态学征象，尽管与非酒精性脂肪肝疾病功能相关的几种蛋白质（胎球蛋白B，视黄醇结合蛋白4，几种线粒体蛋白）的含量增加了。此外，缺乏GHR的肝脏样本显示蛋氨酸和谷胱甘肽代谢途径发生了明显变化，特别是甘氨酸N-甲基转移酶水平显着增加，总和游离谷胱甘肽水平增加。几种蛋白质在对照组中显示出性别相关的丰度差异，而在GHR -KO组中则没有。

结论

我们对来自临床相关大型动物模型的GHR缺乏和对照肝样品进行的蛋白质组学/靶向代谢组学研究，确定了在没有GH作用的情况下显着改变的一系列生物途径。此外，提供了有关GH在性别相关的肝功能指标中的作用的新见解。