The impact of growth hormone on proteomic profiles: a review of mouse and adult human studies

Clinical Proteomics Duran‑Ortiz et al. Clin Proteom (2017) 14:24 DOI 10.1186/s12014-017-9160-2 Open Access REVIEW The impact of growth hormone on proteomic profiles: a review of mouse and adult human studies Silvana Duran‑Ortiz1,2,3†, Alison L. Brittain1,2,3,4† and John J. Kopchick1,3,4* Abstract Growth hormone (GH) is a protein that is known to stimulate postnatal growth, counter regulate insulin’s action and induce expression of insulin-like growth factor-1. GH exerts anabolic or catabolic effects depending upon on the tar‑ geted tissue. For instance, GH increases skeletal muscle and decreases adipose tissue mass. Our laboratory has spent the past two decades studying these effects, including the effects of GH excess and depletion, on the proteome of several mouse and human tissues. This review first discusses proteomic techniques that are commonly used for these types of studies. We then examine the proteomic differences found in mice with excess circulating GH (bGH mice) or mice with disruption of the GH receptor gene (GHR−/−). We also describe the effects of increased and decreased GH action on the proteome of adult patients with either acromegaly, GH deficiency or patients after short-term GH treat‑ ment. Finally, we explain how these proteomic studies resulted in the discovery of potential biomarkers for GH action, particularly those related with the effects of GH on aging, glucose metabolism and body composition. Keywords: Growth hormone, Human proteomics, Mouse proteomics, Aging, GHR−/− mice, bGH mice, Growth hormone deficiency, Acromegaly, Growth hormone doping Background Growth hormone (GH) is a peptide hormone secreted by somatotrophic cells of the anterior pituitary. GH has both anabolic and catabolic effects in its role as a regulator of postnatal growth and metabolism. For instance, GH promotes adipose tissue (AT) lipolysis while inducing protein synthesis in skeletal muscle, and bone growth via chondrocyte expansion in bone. GH exerts its actions by interacting with the GH receptor (GHR) and stimulating a variety of intracellular signaling pathways [1]. Cells of most tissues express GHRs on their surface; therefore GH affects most cells/tissues in the body [2]. One of the many proteins induced by GH is insulin-like growth factor-I (IGF-I), a potent growth factor that also affects many cell types. High circulating levels of IGF-I *Correspondence: † Silvana Duran-Ortiz and Alison L. Brittain contributed equally to this work 4 Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH 45701, USA Full list of author information is available at the end of the article down regulate the release of GH by the anterior pituitary, a relationship that helps to define the GH/IGF-I axis (Fig. 1). Importantly, GH has both direct and indirect (via IGF-I) effects on animal growth. For example, 14% of mouse growth is a result of GH action; IGF-I promotes 35% of mouse growth; the combined action of GH and IGF-I supports 34% of mouse growth; and other factors contribute the remaining 17% to total mouse growth. Thus, GH and IGF-I have both unique and overlapping functions in terms of growth [3]. For over two decades, our laboratory has focused a portion of its research efforts on understanding GH action and its complex relationship to growth, diabetes and aging. These efforts have led us to several landmark findings including: (1) the discovery of GHR antagonists and (2) generation of the GHR gene disrupted mouse; the longest-lived laboratory mouse [4–8]. Included in these endeavors was an exploration into the proteomic fluctuations in a variety of human and mouse tissues as a function of GH action. © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Duran‑Ortiz et al. Clin Proteom (2017) 14:24 Page 2 of 22 Fig. 2 Sample 2D gel. Representative 2D gel of skin proteins in C57BL/6J mice. Image courtesy of Dr. Edward List Fig. 1 General overview of the GH/IGF-I axis. GH is secreted from the anterior pituitary in response to hypothalamic stimulus and has effects on many tissues in the body, including stimulating large amounts of IGF-I secretion by the l and other tissues. Increases in cir‑ culating IGF-I negatively impact GH release from the pituitary gland The aim of this review is to highlight key differences in the proteomes of several GH responsive tissues in both humans and mice. We will specifically focus on studies conducted in our laboratory using both adult humans and mouse lines with GH excess or deficiency. Prior to this undertaking, we will review techniques commonly used in the exploration of proteome composition, particularly concerning models of GH action, diabetes and aging. Through these efforts, we hope to provide a thorough and useful tool of reference for researchers working in these fields. Main text Proteomic techniques The application of proteomics can be accomplished through variety of techniques including the use of antibody-based assays like the enzyme-linked immunosorbent assay (ELISA) and western blotting (WB), as well as mass spectrometry (MS) and protein arrays [9]. Another popular method is 2-dimensional gel electrophoresis (2DE), a technique that separates proteins in a sample by their isoelectric point (first dimension) and their molecular mass (second dimension). An example of a 2DE gel of proteins extracted from mouse skin is shown in Fig. 2. Although 2DE provides valuable proteomic information, it has several limitations, including difficulty with gel reproducibility, inefficiency at detecting hydrophobic proteins and proteins in low abundance, and difficulty spotting proteins with extreme molecular weights (<10 and >150 kD) or outermost pH values (pH < 3 and pH > 10) [10]. Despite these limitations, 2DE is a widelyused technique for profiling proteins and is the basis for the experiments discussed in this review. Proteins can be separated via methods other than gel electrophoresis, including high-performance liquid chromatography (HPLC). This process relies upon pressurization by pumps, to drive a biological sample through a column, separating proteins on the basis of protein interactions with the column matrix. Protein separation by HPLC allows for a much higher resolution during the MS procedure and reduces the potential overlap between peaks of proteins occurring at the same mass. More detailed reviews of the LC–MS procedure and other types (...truncated)